http://hdl.handle.net/1811/5850 2013-05-24T01:30:07Z 2013-05-24T01:30:07Z Neill, Justin L. Perez, Cristobal Muckle, Matt T. Pate, Brooks H. Pena, Isabel Lopez, Juan C. Alonso, Jose L. http://hdl.handle.net/1811/52611 2012-12-29T07:56:56Z 2012-01-01T00:00:00Z

STRUCTURE OF HIGH-ORDER WATER CLUSTERS OF $\beta$-PROPIOLACTONE BY BROADBAND MICROWAVE SPECTROSCOPY Neill, Justin L.; Perez, Cristobal; Muckle, Matt T.; Pate, Brooks H.; Pena, Isabel; Lopez, Juan C.; Alonso, Jose L. The rotational spectra of $\beta$-propiolactone-(H$_2$O)$_n$ (n=1-5) adducts have been extensively analyzed by broadband microwave spectroscopy (CP-FTMW). Unambiguous identification of their structures has been achieved from the spectra of the parent species and H$_2^{18}$O single substitution clusters and Stark effect measurements. In addition to our previous work, the substitution structures for two n=4 and one n=5 complexes are presented. The three structures show a cyclic arrangement in the oxygen framework. For both n=4 structures, the water molecules form a quasiplanar ring that sits above the BPL unit. The structural differences between these two n=4 complexes are discussed in terms of the water oxygen atom positions and dipole moment orientations, enabling to distinguish between isomers with certainty by CP-FTMW spectroscopy. For n=5, a cyclic arrangement similar to n=4 was found with water molecules making a puckered five-water ring. Substitution coordinates for the oxygen framework support the assignment. Our results show that complexation with BPL induces measurable structural changes in the (H$_2$O)$_n$ (n = 3, 4, 5) pure water clusters. This fact is also discussed in terms of the variation in O-O distances within pure and complexed water clusters. Author Institution: University of Michigan. Department of Astronomy 830 Dennison Bldg. 500 Church St. Ann Arbor, MI 48109-1042; Department of Chemistry, University of Virginia, McCormick Rd.; Charlottesville, VA 22904; Grupo de Espectroscopia Molecular (GEM). Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia.; Parque Cientifico Uva Universidad de Valladolid. 47011 Valladolid, Spain

2012-01-01T00:00:00Z Neill, Justin L. Perez, Cristobal Muckle, Matt T. Pate, Brooks H. Pena, Isabel Lopez, Juan C. Alonso, Jose L. Seifert, Nathan A. Zaleski, Daniel P. Neill, Justin L. Pate, Brooks H. Lesarri, Alberto Vallejo, Montserrat Cocinero, Emilio J. Castano, Fernando http://hdl.handle.net/1811/52610 2012-12-29T08:05:39Z 2012-01-01T00:00:00Z

STRUCTURE OF THE SEVOFLURANE-BENZENE COMPLEX AS DETERMINED BY CHIRPED-PULSE FTMW SPECTROSCOPY Seifert, Nathan A.; Zaleski, Daniel P.; Neill, Justin L.; Pate, Brooks H.; Lesarri, Alberto; Vallejo, Montserrat; Cocinero, Emilio J.; Castano, Fernando Following previous microwave studies on sevoflurane monomer by Suenram \textit{et al.} and Vega-Toribio \textit{et al.} we report the broadband rotational spectrum of sevoflurane clustered with benzene. The structure assigned is consistent with a C-H$\cdots\pi$ interaction between the benzene ring and the (CF$_3$)$_2$C-H hydrogen on sevoflurane. The spectrum of this species is complicated by the six-fold internal rotation of the benzene ring over the C$_1$ framework of sevoflurane. The six-fold tunneling falls into a high effective barrier case where there are several bound torsional levels. The tunneling spectrum has been successfully analyzed using the BELGI internal rotation program and a barrier to internal rotation of the benzene against sevoflurane of 32.5 cm$^{-1}$ has been determined. Structural information about the complex has been obtained by studying the complex of sevoflurane with benzene-\textit{d$_1$}. For this complex, six unique isomers are observed making it possible to determine the positions of the benzene H-atoms in the complex. Combination of these hydrogen r$_s$ positions with the sevoflurane monomer r$_s$ coordinates reported by Lesarri \textit{et al.} results in a substitution structure in excellent agreement with the ab initio results. Finally, initial microwave results on two sevoflurane dimer species will also be presented. Author Institution: Department of Chemistry, University of Virginia, McCormick Rd.; Charlottesville, VA 22904-4319; Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Valladolid, Spain; Departamento de Quimica Fisica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco (UPV/EHU), Campus de Leioa, Ap. 644, E-48080 Bilbao, Spain

2012-01-01T00:00:00Z Seifert, Nathan A. Zaleski, Daniel P. Neill, Justin L. Pate, Brooks H. Lesarri, Alberto Vallejo, Montserrat Cocinero, Emilio J. Castano, Fernando Howard, B. J. Steer, E. Page, F. Tayler, M. Ouyang, B. Leung, H. O. Marshall, M. D. Muenter, J. S. http://hdl.handle.net/1811/52609 2012-12-29T07:59:42Z 2012-01-01T00:00:00Z

MICROWAVE SPECTROSCOPY AND PROTON TRANSFER DYNAMICS IN THE FORMIC ACID-ACETIC ACID DIMER Howard, B. J.; Steer, E.; Page, F.; Tayler, M.; Ouyang, B.; Leung, H. O.; Marshall, M. D.; Muenter, J. S. The rotational spectrum of the doubly hydrogen-bonded \textit{hetero} dimer formed between formic acid and acetic acid has been recorded between 4 and 18 GHz using a pulsed-nozzle Fourier transform microwave spectrometer. Each rigid-molecule rotational transition is split into four as a result of two concurrent tunnelling motions, one being proton transfer between the two acid molecules, and the other the torsion/rotation of the methyl group within the acetic acid. We present a full assignment of the spectrum for \textit{J} = 1 to \textit{J} = 7 for these four torsion/tunnelling states. Spectra have been observed for the main isotopic species , \textbf{134}, 054316 (2011).}, with deuterium substitution at the C of the formic acid and all $^{13}$C species in natural abundance, The observed transitions are fitted to within a few kilohertz using a molecule-fixed effective rotational Hamiltonian for the separate \textit{A} and \textit{E} vibrational species of the G$_{12}$ permutation-inversion group which is applicable to this complex. To reduce the effects of internal angular momentum, a non-principal axis system is used throughout. Interpretation of the internal motion uses an internal-vibration and overall rotation scheme, and full sets of rotational and centrifugal distortion constants are determined. \noident The proton tunnelling rates and the internal angular momentum of the methyl group in the \textit{E} states is interpreted in terms of a dynamical model which involves coupled proton transfer and internal rotation. The resulting potential energy surface not only describes these internal motions, but can also explain the observed shifts in rotational constants between \textit{A} and \textit{E} species, and the deviations of the tunnelling frequencies from the expected 2:1 ratio. It also permits the determination of spectral constants free from the contamination effects of the internal dynamics. Author Institution: Department of Chemistry, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom; Department of Chemistry, Amherst College, Amherst, MA 01002; Department of Chemistry, University of Rochester, Rochester, NY 14627

2012-01-01T00:00:00Z Howard, B. J. Steer, E. Page, F. Tayler, M. Ouyang, B. Leung, H. O. Marshall, M. D. Muenter, J. S. Kawashima, Yoshiyuki Moritani, Takayuki Hirota, Eizi http://hdl.handle.net/1811/52608 2012-07-09T19:56:35Z 2012-01-01T00:00:00Z

FOURIER TRANSFORM MICROWAVE SPECTRUM OF CO${_2}$ -(CH${_3}$)${_2}$ S Kawashima, Yoshiyuki; Moritani, Takayuki; Hirota, Eizi In spite of the fact that the oxygen and sulfur atoms belong to the same group in the periodic table, oxygen-containing molecules and their corresponding sulfur analogues often exhibit characteristic differences in their chemical and physical properties. We have been interested in these differences and have investigated, in a systematic way using Fourier transform microwave (FTMW) spectroscopy combined with ab initio molecular orbital calculations, complexes consisting of dimethyl ether (DME)/dimethyl sulfide (DMS) and ethylene oxide (EO)/ ethylene sulfide (ES), each being attached to either one of rare gas atoms (Rg), CO, N${_2}$, or CO${_2}$ nderline{\textbf{116}}, 1224 2012.}. Among others the CO${_2}$-DMS complex should be mentioned, which, in sharp contrast with its counterpart: CO${_2}$-DME nderline{\textbf{108}}, 11234 2004.}. behaves anomalously, presumably because of low-frequency internal motions, and we have decided to explore it in detail by a FTMW spectrometer. We have generated the CO${_2}$-DMS complex by supersonic expansion of a CO${_2}$ and DMS mixture diluted with Ar, and have scanned the frequency region from 5 to 24 GHz to record the rotational spectra of the complex. We have found it difficult to fit the observed transition frequencies to the ordinary rotational Hamiltonian, but have succeeded to assign 75 transitions by sum rules among the observed transition frequencies. We are suspecting the anomalous behavior of the complex to be caused by a low-frequency torsion of the moieties. In the case of the CO${_2}$-DME, the internal rotations of the two methyl groups of the DME were shown to be locked to the CO${_2}$ by hydrogen bonding, whereas, for the CO${_2}$-DMS, we have observed internal-rotation splittings of the two methyl groups of the DMS, indicating the structure of the CO${_2}$-DMS complex being considerably different from that of the CO${_2}$-DME. We will report the structure at the potential minima and the internal motion of the CO${_2}$-DMS, in comparison with the results predicted by quantum chemical calculations. Author Institution: Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of; Technology, Atsugi, Kanagawa 243-0292, JAPAN; The Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, JAPAN

2012-01-01T00:00:00Z Kawashima, Yoshiyuki Moritani, Takayuki Hirota, Eizi Walker, N. R. Stephens, S. L. Legon, A. C. http://hdl.handle.net/1811/52607 2012-12-29T07:56:54Z 2012-01-01T00:00:00Z

MICROWAVE SPECTRA, MOLECULAR STRUCTURES AND INTERNAL DYNAMICS OF H$_{2}$S$\cdots$ICF$_{3}$ and H$_{2}$O$\cdots$ICF$_{3}$ REVEALED BY BROADBAND ROTATIONAL SPECTROSCOPY Walker, N. R.; Stephens, S. L.; Legon, A. C. The rotational spectra of three isotopologues of H$_{2}$S$\cdots$ICF$_{3}$ and four isotopologues of H$_{2}$O$\cdots$ICF$_{3}$ have been measured between 7 and 18.5 GHz by chirped-pulse Fourier transform microwave spectroscopy. The rotational constant, {\it{B}}$_{0}$, the centrifugal distortion constants, {\it{D}}$_{\it{J}}$ and {\it{D}}$_{\it{JK}}$, and the nuclear quadrupole coupling constant of $^{127}$I, ${\chi}_{aa}$(I), are precisely determined for H$_{2}$S$\cdots$ICF$_{3}$ and H$_{2}$O$\cdots$ICF$_{3}$ by fitting observed transitions to the Hamiltonians appropriate to {\it{symmetric}} tops. The measured rotational constants allow determination of the molecular geometries. The {\it{C}}$_{2}$ axis of H$_{2}$O / H$_{2}$S intersects the {\it{C}}$_{3}$ axis of the CF$_{3}$I sub-unit at the oxygen atom. The {\it{r}}$_{0}$ lengths of halogen bonds identified between iodine and sulphur, {\it{r}}{(S$\cdots$I)}, and iodine and oxygen, {\it{r}}(O$\cdots$I), are determined to be 3.5589(2) {\r{A}} and 3.0517(18) {\r{A}} respectively. The angle, $\phi$, between the local {\it{C}}$_{2}$ axis of the H$_{2}$S / H$_{2}$O sub-unit and the {\it{C}}$_{3}$ axis of CF$_{3}$I is found to be 93.7(2)$^irc}$ in H$_{2}$S$\cdots$ICF$_{3}$ and 34.4(20)$^irc}$ in H$_{2}$O$\cdots$ICF$_{3}$. The observed symmetric top spectra imply nearly free internal precession of the {\it{C}}$_{2}$ axis of the hydrogen sulphide/water unit about the {\it{C}}$_{3}$ axis of CF$_{3}$I in each of these complexes. Additional transitions of H$_{2}$$^{16}$O$\cdots$ICF$_{3}$, D$_{2}$$^{16}$O$\cdots$ICF$_{3}$ and H$_{2}$$^{18}$O$\cdots$ICF$_{3}$ can only be assigned using Hamiltonians appropriate to asymmetric tops, suggesting that the effective rigid-rotor fits employed do not completely represent the internal dynamics of H$_{2}$O$\cdots$ICF$_{3}$. Author Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K.

2012-01-01T00:00:00Z Walker, N. R. Stephens, S. L. Legon, A. C. Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. http://hdl.handle.net/1811/52606 2012-12-29T07:56:51Z 2012-01-01T00:00:00Z

MICROWAVE SPECTRA AND GEOMETRIES OF H$_{2}$C$_{2}$$\cdots$AgCl AND H$_{2}$C$_{2}$$\cdots$CuCl Walker, N. R.; Stephens, S. L.; Mizukami, W.; Tew, D. P.; Legon, A. C. Pure rotational spectra of the vibrational ground states of H$_{2}$C$_{2}$$\cdots$AgCl and H$_{2}$C$_{2}$$\cdots$CuCl have been measured by chirped-pulse FTMW spectroscopy. Each complex is generated via laser ablation of the metal in the presence of small percentages of CCl$_{4}$ and C$_{2}$H$_{2}$ in argon. The complexes are stabilized and interrogated in the cold environment of a supersonic jet. Rotational constants ({\it{B}}$_{0}$, {\it{C}}$_{0}$) and the centrifugal distortion constant, $\Delta$$_{\it{J}}$, have been measured for six isotopologues of H$_{2}$C$_{2}$$\cdots$AgCl and three isotopologues of H$_{2}$C$_{2}$$\cdots$CuCl with substitutions at the metal, chlorine and carbon atoms in each case. The spectrum of each complex is consistent with a {\it{C}}$_{2v}$ structure in which the metal atom is coordinated by the ${\pi}$-orbital of ethyne. The measured rotational constants allow determination of the length of the bond between the metal and chlorine atoms, {\it{r}}(M{\textemdash}Cl), and the distance between the metal atom and the centre of the ethyne double bond, {\it{r}}(M{\textemdash}*). Nuclear quadrupole coupling constants have been measured for the chlorine atom in each complex and also for copper in H$_{2}$C$_{2}$$\cdots$CuCl. Author Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K.

2012-01-01T00:00:00Z Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. Guirgis, Gamil A. Gause, Korreda K. Seifert, Nathan A. Zaleski, Daniel P. Pate, Brooks H. Palmer, Michael H. Peebles, Rebecca A. Peebles, Sean A. Elmuti, Lena F. Obenchain, Daniel A. http://hdl.handle.net/1811/52605 2012-12-29T08:00:39Z 2012-01-01T00:00:00Z

STRUCTURAL STUDIES OF CH$_3$SiF$_2$-X (X = NCO, Cl) BY MICROWAVE SPECTROSCOPY Guirgis, Gamil A.; Gause, Korreda K.; Seifert, Nathan A.; Zaleski, Daniel P.; Pate, Brooks H.; Palmer, Michael H.; Peebles, Rebecca A.; Peebles, Sean A.; Elmuti, Lena F.; Obenchain, Daniel A. The structures of CH$_3$SiF$_2$-NCO and CH$_3$SiF$_2$-Cl have been studied by molecular rotational spectroscopy in the 6.5-18 GHz band. The rotational spectrum was measured by cavity Fourier transform microwave (FTMW) and chirped-pulse FTMW spectroscopy. The experiment targeted the study of CH$_3$SiF$_2$-NCO, but CH$_3$SiF$_2$-Cl was also observed as an impurity. Due to the dynamic range achieved on these spectra, all isotopologs with natural abundance $\ge$0.2$\%$ were assigned, which includes two doubly-substituted isotopologs for the chloride ($^{29}$Si/$^{37}$Cl and $^{30}$Si/$^{37}$Cl). Strategies for obtaining the molecular structure for these two molecules using either a Kraitchman analysis (to obtain a partial substitution structure) or $r_0$ analysis (with additional constraints on the structure supplied by the theoretical structure) will be discussed. Derived structural parameters for the CH$_3$-SiF$_2$-X base structure are the same for the two compounds. The hyperfine and internal rotation effects in the spectra have been analyzed for all isotopologs and the Hamiltonian parameters are in very good agreement with ab initio results. The barriers to methyl group internal rotation for the two compounds 446(50) cm$^{-1}$ and 463(3) cm$^{-1}$ and are independent of the isotopic structure of the heavy atom frame. Author Institution: Department of Chemistry & Biochemistry, College of Charleston, Charleston, SC 29424 USA; Department of Chemistry, University of Virginia, McCormick Rd.; Charlottesville, VA 22904-4319; School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK; Department of Chemistry, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL, 61920 USA

2012-01-01T00:00:00Z Guirgis, Gamil A. Gause, Korreda K. Seifert, Nathan A. Zaleski, Daniel P. Pate, Brooks H. Palmer, Michael H. Peebles, Rebecca A. Peebles, Sean A. Elmuti, Lena F. Obenchain, Daniel A. Elmuti, Lena F. Obenchain, Daniel A. Peebles, Rebecca A. Peebles, Sean A. http://hdl.handle.net/1811/52604 2012-12-29T07:56:46Z 2012-01-01T00:00:00Z

ANALYSIS OF MICROWAVE SPECTRUM, INTERNAL ROTATION AND C--H$ \cdots $F INTERACTIONS OF THE CHF$_3 \cdots $C$_2$H$_3$F WEAKLY BOUND COMPLEX Elmuti, Lena F.; Obenchain, Daniel A.; Peebles, Rebecca A.; Peebles, Sean A. C--H$ \cdots $X hydrogen bonds with systematic variation of halogens (X = F, Cl, Br) have been examined using Fourier-Transform Microwave (FTMW) spectroscopy. Rotational constants for trifluoromethane--vinyl fluoride (TFM$\cdots$VF) were consistent with a $C_{\textrm s}$ symmetry structure that exhibited both bifurcated and single C--H$ \cdots $F interactions between the TFM and VF. This near prolate asymmetric top exhibited three-fold internal rotation of the CF$_3$ group causing characteristic doubling in its spectra. Initial assignments were completed using chirped-pulse FTMW spectroscopy with additional measurements made using a resonant-cavity FTMW spectrometer. Rotational constants from ab initio calculations at the MP2/6-311++G(2d,2p) level were in agreement with preliminary experimental values ($A= 4828$ MHz, $B = 1049$ MHz, $C= 1018$ MHz). XIAM, nderline{\textbf {51a}}, (1996), 923-932.} was used to provide the barrier to internal rotation ($25(5)$ cm$^{-1}$) and other spectral information. Spectroscopic parameters for the normal isotopic species as well as preliminary structural results on the C--H$ \cdots $F interactions in this complex will be presented. Author Institution: Department of Chemistry, Eastern Illinois University, 600 Lincoln; Ave., Charleston, IL 61920

2012-01-01T00:00:00Z Elmuti, Lena F. Obenchain, Daniel A. Peebles, Rebecca A. Peebles, Sean A. Peebles, Rebecca A. Thomas, Amelia J. Serafin, Michal M. Peebles, Sean A. http://hdl.handle.net/1811/52603 2012-12-29T08:01:04Z 2012-01-01T00:00:00Z

STRUCTURE AND INVERSION MOTIONS OF THE WEAKLY BOUND CH$_2$F$_2 \cdots $CO$_2$ DIMER Peebles, Rebecca A.; Thomas, Amelia J.; Serafin, Michal M.; Peebles, Sean A. The rotational spectrum of the CH$_2$F$_2 \cdots $CO$_2$ dimer has been measured using chirped-pulse and resonant cavity Fourier-transform microwave (FTMW) spectroscopy, with the broadband spectrum playing an essential role in allowing identification of the tunneling splittings. The observed $a$-type transitions were doubled by a few megahertz, while $c$-type transitions were split by around 200 MHz, suggesting a tunneling motion that inverts the $\mu_c$ dipole moment component. A Pickett-type coupled Hamiltonian has been used to analyze the spectra, giving an energy difference ($\Delta E$) between the tunneling states for the normal isotopologue of $115.140(2)$ MHz, and rotational constants of $A_0 = 5567.8604(27)$ MHz, $B_0 = 1832.9676(5)$ MHz, $C_0 = 1828.6132(5)$ MHz, $A_1 = 5567.8540(26)$ MHz, $B_1 = 1831.7711(4)$ MHz, $C_1 = 1828.6106(4)$ MHz. It was also necessary to include a Coriolis coupling term ($G_b = 7.740(6)$ MHz) as well as fourth and sixth order centrifugal distortion constants to obtain a satisfactory spectroscopic fit. The rotational constants and planar moments are consistent with a $C_s$ symmetry structure in which the $C_2$ axis of CH$_2$F$_2$ makes an angle of roughly $23^irc$ with the axis of the CO$_2$, with the fluorine atoms of CH$_2$F$_2$ straddling the CO$_2$ carbon atom. The spectra of five additional isotopologues were analyzed, providing detailed structural information, and all except the mixed C$^{18}$O$^{16}$O species showed inversion splittings similar to the normal species. The observation of unsplit spectra for two distinct C$^{18}$O$^{16}$O isotopologues confirms that the internal motion involves movement of the CH$_2$F$_2$ subunit between the two ends of the CO$_2$ molecule. Author Institution: Department of Chemistry, Eastern Illinois University, 600 Lincoln; Ave., Charleston, IL 61920

2012-01-01T00:00:00Z Peebles, Rebecca A. Thomas, Amelia J. Serafin, Michal M. Peebles, Sean A. Oyama, Takahiro Nakajima, Masakazu Endo, Yasuki Sumiyoshi, Yoshihiro http://hdl.handle.net/1811/52602 2012-12-29T08:00:54Z 2012-01-01T00:00:00Z

OBSERVATION OF THE PURE ROTATIONAL SPECTRA OF THE H$_2$O-$trans$-HOCO COMPLEX Oyama, Takahiro; Nakajima, Masakazu; Endo, Yasuki; Sumiyoshi, Yoshihiro Rotational spectra of the H$_2$O-\textit{trans}-HOCO complex have been observed using a Fourier transform microwave (FTMW) spectrometer. The complex was produced in a supersonic jet by discharging a gas mixture of CO and H$_{2}$O diluted in Ar. The observed lines show that the ground state of the complex is split into two by the exchange symmetry of the two equivalent protons of H$_2$O. The molecular constants including the hyperfine coupling constants have been precisely determined for the two states. The Fermi contact constants of the two states are smaller than that of the \textit{trans}-HOCO monomer. This result indicates that there is an induced effect for the spin density on the hydrogen nucleus of HOCO by the complex formation. Author Institution: Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902, Japan; Department of Chemistry and Chemical Biology, Gunma University, 4-2 Aramaki-machi, Maebashi City, Gunma, 371-8510 Japan

2012-01-01T00:00:00Z Oyama, Takahiro Nakajima, Masakazu Endo, Yasuki Sumiyoshi, Yoshihiro Benner, D. Chris Devi, V. Malathy O'Brien, J. J. Shaji, S. Spickler, P. T. Houck, C. P. Coakley, J. A. Dolph, J. Rankin, K. http://hdl.handle.net/1811/52601 2012-12-29T08:00:46Z 2012-01-01T00:00:00Z

LINE BY LINE SPECTRAL PARAMETERS IN THE $4\nu_3$ SPECTRAL REGION OF METHANE Benner, D. Chris; Devi, V. Malathy; O'Brien, J. J.; Shaji, S.; Spickler, P. T.; Houck, C. P.; Coakley, J. A.; Dolph, J.; Rankin, K. The near infrared bands of methane were first observed in the outer planets and Titan where atmospheric ray paths are long. The spectrum is complex, and long absorption paths in the laboratory are difficult to cool to outer solar system temperatures. At room temperature, many significant spectral lines appear per Doppler width. The band models generally used in the 890 nm spectral region of methane do not provide transmissions that are multiplicative, so scattering and inhomogeneous atmospheres cannot be properly treated using this approach. \vspace{1em} The intracavity laser spectrometer at the University of Missouri-St.~Louis was used to obtain low temperature (99-161K), low pressure (0.12-7.13 Torr), long path (3.14-5.65 km) and high resolution (~0.01 cm$^{-1}$ HWHM) spectra of methane covering the entire 890nm feature (10925-11500 cm$^{-1}$), the deepest band in the CCD spectral region. At these temperatures the Doppler width is 0.01 cm$^{-1}$ and the spectral lines originating from levels higher than J"=11 and excited vibrational states are not visible. The result is a dense, but manageable spectrum from which over 11,200 line positions, intensities and lower state energies are derived on a line by line basis by the College of William and Mary multispectrum nonlinear least squares fitting program. Simulations of the methane spectrum for outer planet atmospheres using our positions, intensities and lower state energies reveal a surprising amount of spectral structure at high resolution. This structure carries a great deal of atmospheric information. Author Institution: Department of Physics, College of William and Mary, Williamsburg, VA 23187-8795; Department of Chemistry, University of Missouri - St. Louis, St. Louis, MO 63121-4400; Department of Physics, Bridgewater College, Bridgewater, VA 22812

2012-01-01T00:00:00Z Benner, D. Chris Devi, V. Malathy O'Brien, J. J. Shaji, S. Spickler, P. T. Houck, C. P. Coakley, J. A. Dolph, J. Rankin, K. Niida, Chisato Nakajima, Masakazu Endo, Yasuki Sumiyoshi, Yoshihiro Ohshima, Yasuhiro Kohguchi, Hiroshi http://hdl.handle.net/1811/52600 2012-12-29T08:01:01Z 2012-01-01T00:00:00Z

FTMW SPECTROSCOPY AND DETERMINATION OF THE 3-D POTENTIAL ENERGY SURFACE FOR Ar-CS Niida, Chisato; Nakajima, Masakazu; Endo, Yasuki; Sumiyoshi, Yoshihiro; Ohshima, Yasuhiro; Kohguchi, Hiroshi Pure rotational transitions of the Ar-CS complex have been observed by FTMW spectroscopy for the normal species with v$_{CS} = 0, 1, 2$ and for C$^{34}$S in the ground vibrational state. All the observed transition frequencies have been utilized to determine a 3-Dimentional potential energy surface for the complex, explicitly considering the dependence of the CS stretcing for the intermolecular potential between Ar and CS, which is indispensable to analyze the transitions for the excited vibrational states and those of the $^{34}S$ species simultaneously. High-level \textit{ab initio} calculations have been performed to obtain the initial 3-D potential. The \textit{ab initio} poteintial has been fitted to an analytical function with determinable parameters. The parameters have been improved by fitting the observed transition frequencies. All the observed transition frequencies have successfully been fitted almost within their experimental accuracies. Author Institution: Department of Basic Science, The University of Tokyo, Tokyo 153-8902, Japan; Department of Chemistry and Chemical biology, Gunma University, Maebashi; Gunma, 371-8510, Japan; Department of Photo-Molecular Science, Institute for Molecular Science, Okazaki, 444-8585, Japan; Department of Chemistry, Hiroshima University, Higashi-Hiroshima, 739-8511, Japan

2012-01-01T00:00:00Z Niida, Chisato Nakajima, Masakazu Endo, Yasuki Sumiyoshi, Yoshihiro Ohshima, Yasuhiro Kohguchi, Hiroshi Howard, Brian J. Economides, George Dyer, Lee http://hdl.handle.net/1811/52599 2012-12-29T08:00:59Z 2012-01-01T00:00:00Z

MICROWAVE SPECTROSCOPY AND INTERNAL DYNAMICS OF THE Ne-NO$_{2}$ VAN DER WAALS COMPLEX Howard, Brian J.; Economides, George; Dyer, Lee The rotational spectrum of the open-shell complex Ne-NO$_{2}$ in the 6 - 18 GHz region is reported. Both fine and hyperfine structure are observed. However, the spectrum does not fit a semi-rigid model as well as the related species Ar-NO$_{2}$ , \textbf{105}, 6756 (1996).}, Kr-NO$_{2}$ , \textbf{3}, 3895 (2001).} and Xe-NO$_{2}$ , \textbf{286}, 408 (1998).}. This is almost certainly a result of the "floppy" nature of this species. In order to model the dynamics of the complex and to reproduce the observed spectrum, we have obtained an accurate intermolecular potential surface using the RCCSD(T) method and aug-cc-pV(D/T)Z basis sets (extrapolated to the complete basis set limit). Full quantum dynamics calculations were then performed on this surface to give the rotational energy levels and the effective fine and hyperfine structure constants. Author Institution: Department of Chemistry, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom

2012-01-01T00:00:00Z Howard, Brian J. Economides, George Dyer, Lee Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. http://hdl.handle.net/1811/52598 2012-12-29T08:00:37Z 2012-01-01T00:00:00Z

MICROWAVE SPECTRUM AND GEOMETRY OF H$_{3}$P$\cdots$AgI Walker, N. R.; Stephens, S. L.; Mizukami, W.; Tew, D. P.; Legon, A. C. The pure rotational spectrum of the vibrational ground state of H$_{3}$P$\cdots$AgI has been measured by chirped-pulse FTMW spectroscopy. The complex is generated via laser ablation (532 nm) of a silver rod in the presence of CF$_{3}$I, PH$_{3}$ and argon. It is subsequently stabilized and interrogated in the cold environment of a supersonic jet. The rotational constant, {\it{B}}$_{0}$, and the centrifugal distortion constant, {\it{D}}$_{\it{J}}$, have been measured for H$_{3}$P$\cdots$$^{107}$AgI and H$_{3}$P$\cdots$$^{109}$AgI. The spectrum of the complex is consistent with a {\it{C}}$_{3v}$ geometry and a linear arrangement of the P, Ag and C atoms. The measured rotational constants allow a preliminary determination of the geometry of the molecule. The nuclear quadrupole coupling constant of the iodine atom, ${\chi}_{aa}$(I) , is also established. The experimental results are compared with theory performed at the explicitly-correlated coupled-cluster singles, doubles and perturbative triples level. Author Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K.

2012-01-01T00:00:00Z Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. http://hdl.handle.net/1811/52597 2012-12-29T08:00:55Z 2012-01-01T00:00:00Z

BROADBAND ROTATIONAL SPECTRUM AND MOLECULAR GEOMETRY OF OC $\cdots$AgI Walker, N. R.; Stephens, S. L.; Mizukami, W.; Tew, D. P.; Legon, A. C. Pure rotational spectra of the ground vibrational states of six isotopologues of OC$\cdots$AgI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are assigned to determine the rotational constant, {\it{B}}$_{0}$, and the centrifugal distortion constant, {\it{D}}$_{\it{J}}$, of the complex. The nuclear quadrupole coupling constant of the iodine atom, ${\chi}_{aa}$(I), has also been measured. The complex is linear. The length of the C{\textemdash}O bond, r(CO), in the {\it{r}}$_{0}$ geometry for OC$\cdots$AgI is 0.008 {\r{A}} shorter than that found in the free CO molecule. The length of the Ag{\textemdash}I bond, {\it{r}}(AgI), is 0.013 {\r{A}} shorter than in free AgI. The nuclear quadrupole coupling constant of the iodine atom is determined to be -769.84(22) MHz for OC$\cdots$$^{107}$AgI implying an ionic character of 0.66 for the metal halide bond. The molecular structure and spectroscopic parameters determined from the experimental data are presented alongside the results of calculations at the explicitly-correlated CCSD(T) level. The design features of a laser ablation source constructed for the present work will be described. Author Institution: School of Chemistry, University of Bristol, Bristol, BS8 1TS, U.K.

2012-01-01T00:00:00Z Walker, N. R. Stephens, S. L. Mizukami, W. Tew, D. P. Legon, A. C. Roehr, N. P. Szczepanski, J. Polfer, N. C. http://hdl.handle.net/1811/52596 2012-12-29T08:00:51Z 2012-01-01T00:00:00Z

UV/VIS ABSORPTION EXPERIMENTS ON MASS SELECTED CATIONS BY COUNTER-ION INTRODUCTION INTO AN INERT NEON MATRIX Roehr, N. P.; Szczepanski, J.; Polfer, N. C. Obtaining UV/Vis absorption spectra of cations is a challenging endeavor due to the low densities that can be achieved in the gas phase. In matrix isolation, ions of interest are accumulated in a cold inert matrix of a rare gas (e.g. Argon, Neon) until sufficient concentrations are attained for direct spectroscopic characterization ,~J.~Chem.~Phys.~90,~600(1989).}. Nonetheless, in order to ensure neutralization of the matrix, experimentalists often rely on non-ideal, energetic processes, such as electron emission from metal surfaces upon cation bombardment ,~J.~Phys.~Chem.~100~2892-2899(1996).}. A better method for matrix neutralization would involve co-depositing a molecular counter-ion. In this talk, a two-ion source instrument is presented, where cations and anions are deposited into a cold inert matrix. Mass-selected cation beams are generated in an electron ionization source and filtered in a quadrupole mass filter (5-10 nA mass-selected naphthalene radical cations recorded). Anion beams are generated in a chemical ionization source (20 nA SF$_{6}^{-}$ recorded). Both ion beams are introduced into an octopole ion guide via a quadrupole deflector. Cations and anions can be deposited simultaneously or separately; in the latter case, alternating layers of each species can be formed. Target cations of interest include open-shell naphthalene and tetracene, for which UV/Vis absorption spectra are recorded after deposition ,~J.~Chem.~Phys.~22~7337-7347(1999).}$^{,}$,~Chem.~Phys.~Lett.~245~539-548(1995).}. The counter-ion of choice is SF$_{6}^{-}$, due to the high electronegativity of SF$_{6}$. Author Institution: Department of Chemistry, University of Florida, Gainesville, FL 32608

2012-01-01T00:00:00Z Roehr, N. P. Szczepanski, J. Polfer, N. C. Jacox, Marilyn E. Thompson, Warren E. http://hdl.handle.net/1811/52595 2012-12-29T08:00:43Z 2012-01-01T00:00:00Z

INFRARED STUDY OF THE WATER-HYDROXYL RADICAL COMPLEX TRAPPED IN SOLID NEON Jacox, Marilyn E.; Thompson, Warren E. The most prominent infrared absorptions which appear when a Ne:O$_2$ mixture is codeposited at 4.3 K with a Ne:H$_2$ mixture that has been passed through a microwave discharge are those of H$_2$O, HO$_2$, the HOHOH anion, and the H$_2$O(HO) complex. The absorptions of this complex correspond well with those previously obtained in argon-matrix experiments . Photodetachment of the HOHOH anion leads to extremely great intensification of the absorptions of the H$_2$O(HO) complex. The infrared spectra of the normal and deuterium- substituted complex and the mechanisms of formation and photodestruction of the HOHOH anion will be considered. Author Institution: Sensor Science Division, National Institute of Standards and Technology; Gaithersburg, MD 20899-8441

2012-01-01T00:00:00Z Jacox, Marilyn E. Thompson, Warren E. Jacox, Marilyn E. Thompson, Warren E. http://hdl.handle.net/1811/52594 2012-12-29T08:05:23Z 2012-01-01T00:00:00Z

INFRARED SPECTROSCOPIC EVIDENCE FOR ISOTOPOLOGS OF THE HOHOH ANION TRAPPED IN SOLID NEON Jacox, Marilyn E.; Thompson, Warren E. Although properties of the HOHOH anion have long been sought, only recently have quantum chemical calculations converged on a centrosymmetric structure for it. One vibrational fundamental, the antisymmetric stretching motion of the central H atom along the OHO axis, has even more recently been identified in the gas phase . In experiments involving the codeposition at 4.3 K of a Ne:O$_2$ mixture with a Ne:H$_2$ mixture that has been passed through a microwave discharge, this fundamental absorption appears very close to its gas-phase position. Experiments involving partial and full deuterium enrichment confirm the presence of multiple H atoms in the anion and provide the first observation of the corresponding fundamental of the fully deuterium-substituted species. Author Institution: Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8441

2012-01-01T00:00:00Z Jacox, Marilyn E. Thompson, Warren E. Dunbar, Robert C. Polfer, Nicolas Berden, Giel Oomens, Jos http://hdl.handle.net/1811/52593 2012-12-29T08:05:08Z 2012-01-01T00:00:00Z

METAL ION BINDING TO POLYPEPTIDES CHARACTERIZED BY IRMPD SPECTROSCOPY. METAL-AMIDE NITROGEN BINDING AND THE IMINOL TAUTOMERIZATION. Dunbar, Robert C.; Polfer, Nicolas; Berden, Giel; Oomens, Jos We have recently uncovered a new binding mode for the complexation of metal ions with gas-phase peptides. Termed the iminol mode, this binding mode is adopted by strongly binding divalent metal ions including Mg2+ and Ni2+. The metal ion displaces the amide hydrogen, which moves to protonate the amide carbonyl oxygen. A spectroscopic signature of the tautomerization is the disappearance of the characteristic Amide II band normally seen in peptide ion infrared spectra. We find that in peptides up to pentapeptides, multiple iminol binding can take place, such that all amide linkages are tautomerized to the iminol form, and chelate the metal ion. However, the iminol tautomerization depends on the nature of the metal ion, as will be discussed. Spectra of the ions were acquired by irradiating the cell of the Fourier-transform ion cyclotron resonance mass spectrometer with infrared light from the FELIX laser at wavelengths in the approximate range 500 to 1900 cm$^{-1}$. Author Institution: Chemistry Department, Case Western Reserve Univ., Cleveland, OH 44106; Chemistry Department, University of Florida, Gainesville, FL; FOM Institute for Plasma Physics, Nieuwegein, Netherlands; FOM Institute for Plasma Physics, Nieuwegein, and University of Amsterdam, Netherlands

2012-01-01T00:00:00Z Dunbar, Robert C. Polfer, Nicolas Berden, Giel Oomens, Jos Miyamoto, Y. Ikeda, N. Tang, J. Kawaguchi, K. Masaki, C. http://hdl.handle.net/1811/52592 2012-12-29T08:05:34Z 2012-01-01T00:00:00Z

TIME-RESOLVED FTIR AND MASS SPECTROSCOPY OF LASER-ABLATED MAGNESIUM. Miyamoto, Y.; Ikeda, N.; Tang, J.; Kawaguchi, K.; Masaki, C. Laser-ablated Magnesium (Mg) was subjected to time-resolved Fourier transform emission spectroscopy combined with quadrupole mass spectroscopy. Emission of Mg atoms was observed in 2000 $\sim$ 4000 cm$^{-1}$ region with resolution of 0.03 cm$^{-1}$. It was found that emission lines consist of two components with different Doppler width. One with wider linewidth appeared just after ablation, while the other appeared after about 10 $\mu$s. Doppler width of the narrow one corresponds to estimated velocity of atoms sputtered directly from bulk Mg. Mass spectra suggested major products of the ablation under our experimental conditions are Mg$^+$ and Mg$_{2}$$^{+}$. MgO$^{+}$ was also observed in the mass spectra under thin oxygen condition ($\sim$ 10$^{-4}$ Torr). Considering the linewidth and energy levels of these species, the wide component is attributed to Mg atoms produced by dissociative recombination of MgO$^{+}$ and electrons. Information about the electronic energy level of MgO$^{+}$ was also obtained, which is compared with $\textit{ab initio}$ calculations. Author Institution: Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka Okayama 700-8530, Japan; Faculty of Science, Okayama University, 3-1-1 Tsushima-naka Okayama 700-8530, Japan

2012-01-01T00:00:00Z Miyamoto, Y. Ikeda, N. Tang, J. Kawaguchi, K. Masaki, C. Mosley, J. D. Cheng, T. C. Duncan, M. A. http://hdl.handle.net/1811/52591 2012-12-29T08:05:30Z 2012-01-01T00:00:00Z

INFRARED SPECTROSCOPY OF PROTONATED CARBONYLS: PROTONATED GLYOXAL Mosley, J. D.; Cheng, T. C.; Duncan, M. A. The protonation site of carbonyls is usually at oxygen, allowing studies of the $O-H^+$ and carbonyl stretch vibrations and their variation with the local chemical environment. We have already studied protonated acetone and its proton-bridged dimer and now extend the study of protonated carbonyls to protonated glyoxal. Glyoxal is the simplest $\alpha$-oxoaldehyde, which has the chance to form an intramolecular bridging proton structure upon protonation. Computational chemistry predicts the proton-bridged \emph{cis} isomer to be the lowest energy structure. The infrared spectrum of mass-selected protonated glyoxal is obtained using infrared photodissociation spectroscopy with Ar tagging. The spectrum shows the presence of only the higher energy \emph{trans} isomer when compared with purely harmonic calculations. The frequencies of the $O-H^+$ and carbonyl stretch vibrations of protonated glyoxal are compared to other protonated carbonyls. Author Institution: University of Georgia, Dept. of Chemistry, 1001 Cedar St, Athens, GA 30602

2012-01-01T00:00:00Z Mosley, J. D. Cheng, T. C. Duncan, M. A. Devi, V. Malathy Benner, D. Chris Kleiner, I. Sams, R. L. Blake, T. A. Brown, Linda R. Fletcher, L. N. http://hdl.handle.net/1811/52590 2012-12-29T08:05:02Z 2012-01-01T00:00:00Z

LINE PARAMETERS OF THE PH$_3$ PENTAD IN THE $4-5 \mu$m REGION Devi, V. Malathy; Benner, D. Chris; Kleiner, I.; Sams, R. L.; Blake, T. A.; Brown, Linda R.; Fletcher, L. N. Line positions, intensities and line shape parameters are reported for four bands of phosphine between 2150 and 2400 cm$^{-1}$ in order to improve the spectroscopic database for remote sensing of the giant planets. Knowledge of PH$_3$ in this spectral region is important for Cassini/VIMS exploration of dynamics and chemistry on Saturn, as well as for interpreting the near-IR data from Juno and ESA's proposed Jupiter mission. For this study, five high-resolution (0.0023 cm$^{-1}$), high signal-to-noise (>2000) spectra of pure PH$_3$ were recorded at room temperature (298.2 K) with the Bruker IFS 125HR Fourier transform spectrometer at Pacific Northwest National Laboratory. Individual line parameters were retrieved by multispectrum fitting nderline{\textbf{53}} (1995) 705-721.} of all five spectra simultaneously. Positions and intensities were measured for over 3100 transitions. The rotational quantum numbers of measured lines go as high as $J^{\prime\prime}=16$ and $K^{\prime\prime}=15$ in the $\nu_3$ and $\nu_1$ bands; some lines of the weaker bands $2\nu_4$ and $\nu_2+\nu_4$ are also reported. The measured positions and intensities are compared to new theoretical calculations of the pentad. Lorentz self-broadened width and pressure-induced shift coefficients of many transitions were also obtained, along with speed dependence parameters. Line mixing coefficients were determined for several $A^{+}A^{-}$ pairs of transitions for $K^{\prime\prime}=3, 6$, and $9$. Author Institution: The College of William and Mary, Williamsburg, VA 23187; Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), UMR 7583 CNRS/IPSL-Universites; Paris-ESt and Diderot, 94010 Creteil Cedex, France; Pacific Northwest National Laboratory, Richland, WA 99352; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109; Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK

2012-01-01T00:00:00Z Devi, V. Malathy Benner, D. Chris Kleiner, I. Sams, R. L. Blake, T. A. Brown, Linda R. Fletcher, L. N. Mosley, J. D. Cheng, T. C. Duncan, M. A. http://hdl.handle.net/1811/52589 2012-12-29T08:05:22Z 2012-01-01T00:00:00Z

INFRARED SPECTROSCOPY OF THE MASS 31 CATION: PROTONATED FORMALDEHYDE VS. THE TRIPLET METHOXY CATION Mosley, J. D.; Cheng, T. C.; Duncan, M. A. The m/z=31 cation is produced by ionization and fragmentation of methanol, ethanol, dimethyl ether, etc. Two structures have been proposed, protonated formaldehyde ($^1CH_2OH^+$) and the triplet methoxy cation ($^3CH_3O^+$). The infrared spectrum of the mass 31 cation is obtained using infrared photodissociation spectroscopy with Ar tagging. The spectrum reveals the presence of two stable isomers, protonated formaldehyde ($^1CH_2OH^+$) and the triplet methoxy cation ($^3CH_3O^+$). The triplet methoxy cation has been studied extensively and is predicted to interconvert to protonated formaldehyde through an essentially barrierless process on a timescale much faster than our experiment ($>100$ $\mu$s). The presence of two structural isomers is verified by comparison of spectra from different precursors and spectra of different temperature ions from the same precursor. Author Institution: University of Georgia, Dept. of Chemistry, 1001 Cedar St, Athens, GA 30602

2012-01-01T00:00:00Z Mosley, J. D. Cheng, T. C. Duncan, M. A. Tanaka, Keiichi Harada, Kensuke Nanbu, Shinkoh Oka, Takeshi http://hdl.handle.net/1811/52588 2012-12-29T08:05:11Z 2012-01-01T00:00:00Z

SPONTANEOUS EMISSION BETWEEN ORTHO- AND PARA-LEVELS OF WATER-ION, H$_2$O$^+$ Tanaka, Keiichi; Harada, Kensuke; Nanbu, Shinkoh; Oka, Takeshi Nuclear spin conversion interaction of water ion, H$_2$O$^+$, has been studied to derive spontaneous emission lifetime between {\em ortho}- and {\em para}-levels. H$_2$O$^+$ is a radical ion with the $^2B_1$ electronic ground state. Its off-diagonal electron spin-nuclear spin interaction term, $T_{ab}(S_a\Delta I_b + S_b\Delta I_a)$, connects {\em para} and {\em ortho} levels, because $ \Delta \mbox{\boldmath $I$} = \mbox{\boldmath $I$}_1 - \mbox{\boldmath $I$}_2$ has nonvanishing matrix elements between $I = 0$ and 1. The mixing by this term with $T_{ab}$ = 72 MHz predicted by $ab~initio$ theory in the MRD-CI/Bk level, \textbf{80}, 1485 (1993)} is many orders of magnitude larger than for closed shell molecules because of the large magnetic interaction due to the un-paired electron. Using the molecular constants reported by Murtz et al. by FIR-LMR \textbf{109}, 9744 (1998).}, we searched for {\em ortho} and {\em para} coupling channels below 1000 cm$^{-1}$ with accidental near degeneracy between {\em para} and {\em ortho} levels. For example, hyperfine components of the 4$_{2,2}$($ortho$) and 3$_{3,0}$($para$) levels mix by 1.2 $\times$ 10$^{-3}$ due to their near degeneracy ($\Delta E$ = 0.417 cm$^{-1}$), and give the {\em ortho}-{\em para} spontaneous emission lifetime of about 0.63 year. The most significant low lying 1$_{0,1}$($para$) and 1$_{1,1}$($ortho$) levels, on the contrary, mix only by 8.7 $\times$ 10$^{-5}$ because of their large separation ($\Delta E$ = 16.267 cm$^{-1}$) and give the spontaneous emission lifetime from 1$_{0,1}$($para$) to 0$_{0,0}$($ortho$) of about 100 year.These results qualitatively help to understand the observed high {\em ortho-} to {\em para-} H$_2$O$^+$ ratio of 4.8 $\pm$ 0.5 \textbf{521}, L11 (2010).} toward Sgr B2 but they are too slow to compete with the conversion by collision unless the number density of the region is very low ($n \sim$ 1 cm$^{-3}$) or radiative temperature is very high ($T_r$ $>$ 100 K). Author Institution: Department of Applied Chemistry, National Chiao Tung University, Hsinchu, 30010, TAIWAN; Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, 812-8581 JAPAN; Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka, 812-8581 JAPAN; Department of Materials and Life Sciences, Faculty of Science and Engineering, Sophia University, Tokyo 102-8554, JAPAN; Department of Astronomy and Astrophysics and Department of Chemistry, the Enrico Fermi Institute, the University of Chicago, Chicago, Illinois, 60637, USA

2012-01-01T00:00:00Z Tanaka, Keiichi Harada, Kensuke Nanbu, Shinkoh Oka, Takeshi Siller, Brian Porambo, Michael McCall, Benjamin http://hdl.handle.net/1811/52587 2012-12-29T08:05:33Z 2012-01-01T00:00:00Z

MID-IR DIRECT ABSORPTION/DISPERSION SPECTROSCOPY OF A FAST ION BEAM Siller, Brian; Porambo, Michael; McCall, Benjamin The direct absorption/dispersion ion beam instrument in the near-IR has been extended into the mid-IR using a difference frequency generation (DFG) laser created from combining a Ti:Sapphire laser with a Nd:YAG laser in a periodically poled lithium niobate (PPLN) crystal. The Nd:YAG laser is locked to an iodine hyperfine transition using a dither lock with 3f demodulation, while the Ti:Sapph laser is measured with an optical frequency comb for absolute frequency determination of the mid-IR beam to $<$1~MHz. Detection of ions within the beam is done using NICE-OHMS (noise immune cavity enhanced optical heterodyne molecular spectroscopy) together with velocity modulation of the ion beam for near shot noise limited sensitivity. \vspace{1em} Initial studies are being done with a hydrogenic plasma in an uncooled cold cathode discharge source to observe H$_3^+$ in the ion beam to test the system. Once the instrument is fully characterized in mid-IR operation, we will implement a continuous supersonic expansion discharge source to enable observation of rotationally cold molecules and enable spectroscopy of more complex molecular ion systems. Author Institution: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801

2012-01-01T00:00:00Z Siller, Brian Porambo, Michael McCall, Benjamin Porambo, Michael Siller, Brian Mills, Andrew Perera, Manori Kreckel, Holger McCall, Benjamin http://hdl.handle.net/1811/52586 2012-12-29T08:05:27Z 2012-01-01T00:00:00Z

INITIAL DEVELOPMENT OF HIGH PRECISION, HIGH RESOLUTION ION BEAM SPECTROMETER IN THE NEAR-INFRARED Porambo, Michael; Siller, Brian; Mills, Andrew; Perera, Manori; Kreckel, Holger; McCall, Benjamin Interest in molecular ions stretches across many fields, from combustion to astrochemistry. These ions can be difficult to study spectroscopically in the laboratory, however. Obstacles include the relatively small density of ions produced in samples compared to neutral molecules and high rotational temperatures of the ions (which lead to dilution of the energy levels). To overcome some of these challenges of molecular ion spectroscopy, we are developing a fast ion beam spectrometer system we call Sensitive, Cooled, Resolved Ion BEam Spectroscopy (SCRIBES). This setup will enable the sensitive study of a supersonically cooled ion beam, taking advantage of narrow linewidths, a mass-dependent Doppler shift for mass identification of each spectral line, and on-line mass spectrometry for beam composition studies. Presently, the spectrometer contains an ion beam source that produces ions at high rotational temperature. We have characterized the spectrometer using the near-infrared rovibronic transitions of N$_2^+$, optimizing the sensitivity of the instrument. Furthermore, we have used an optical frequency comb for highly accurate frequency calibration, measuring a N$_2^+$ transition to within an accuracy of 8 MHz. This work in the near-infrared has laid the foundation for mid-infrared and indirect THz ion beam spectroscopy of many interesting molecular ions at a high level of precision, accuracy, and resolution. Author Institution: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801

2012-01-01T00:00:00Z Porambo, Michael Siller, Brian Mills, Andrew Perera, Manori Kreckel, Holger McCall, Benjamin Brathwaite, Antonio D. Duncan, Michael A. http://hdl.handle.net/1811/52585 2012-12-29T08:08:08Z 2012-01-01T00:00:00Z

INFRARED PHOTODISSOCIATION SPECTROSCOPY OF SILICON-CARBONYL CATIONS: EVIDENCE FOR ASSYMETRIC CARBONYL COORDINATION. Brathwaite, Antonio D.; Duncan, Michael A. Cationic silicon carbonyl clusters, consisting of up to twenty carbonyl ligands, are produced via laser vaporization with a pulsed nozzle source and cooled in a supersonic beam. The cations and their argon tagged analogues are mass selected in a reflectron time-of-flight mass spectrometer and studied with infrared laser photodissociation spectroscopy near the free molecular CO vibration (2143 cm$^{1}$). Silicon carbonyl complexes having more than two ligands fragment by loss of CO, whereas the argon tagged complexes fragment by loss of argon. All clusters have resonances near the free molecular CO stretch that provide distinctive patterns from which information on their structure and bonding can be obtained. The number of infrared-active bands, their frequency positions and relative intensities, indicate that species larger than n=2 consist of an asymmetrically coordinated Si(CO)$_{2}^{+}$ core with additional CO ligands attached via van der Waals interactions. Density functional theory computations are carried out in support of the experimental spectra. Author Institution: Department of Chemistry, University of Georgia, Athens, GA 30602-2256

2012-01-01T00:00:00Z Brathwaite, Antonio D. Duncan, Michael A. Duxbury, G. Jungen, Ch. Alijah, A. http://hdl.handle.net/1811/52584 2012-12-29T08:04:56Z 2012-01-01T00:00:00Z

RENNER-TELLER COUPLING IN H$_{2}$S+: A COMPARISON OF THEORY WITH OPTICAL SPECTRA AND RECENT PFI AND MATI EXPERIMENTAL RESULTS Duxbury, G.; Jungen, Ch.; Alijah, A. Most of the early studies of H$_{2}$S+ focussed on the comparison between the medium resolution photoelectron spectra of hydrogen sulphide with the emission spectrum of the A-X emission spectrum of the ion. Recently, with the advent of improved photoelectron and pulsed field ionisation spectrometers, and also a mass-analysed threshold ionisation approach, there has been a renewal of interest in the spectroscopy and dynamics of the formation and the fragmentation of the hydrogen sulphide ion. In this contribution we compare the results derived from these new experiments with the analysis of the original emission spectra. The results are also compared with the predictions made using the stretch-bender approach to the calculation of the effects on the Renner-Teller coupling of large amplitude vibrational motion. Author Institution: Department of Physics, SUPA, John Anderson Building, University of; Strathclyde, 107 Rottenrow, Glasgow G4 0NG, Scotland, UK; LAC, 1 Laboratoire Aime Cotton du CNRS, Universite de Paris-Sud, 91405 Orsay, France; GSMA, UMR CNRS 6089, Universite de Reims Champagne-Ardenne, B.P. 1039, 51687 Reims Cedex 2, France

2012-01-01T00:00:00Z Duxbury, G. Jungen, Ch. Alijah, A. Duxbury, G. Jungen, Ch. Alijah, A. http://hdl.handle.net/1811/52583 2012-12-29T08:04:52Z 2012-01-01T00:00:00Z

RENNER-TELLER COUPLING IN H$_{2}$S+: PARTITIONING THE ROVIBRONIC AND SPINORBIT COUPLING HAMILTONIAN Duxbury, G.; Jungen, Ch.; Alijah, A. The stretch-bender reference-frame was developed to allow the separation of large amplitude bending motion and symmetric stretching. It has been used to calculate vibrational resonances, the effects of spin-orbit coupling, and of overall rotation. Its use allows the block factorisation of the Renner-Teller interaction matrix. We wish to show the utility of this approach when two different approaches by Dixon and Duxbury, and Jungen and Merer, are used to minimise the effects of the large amplitude bending upon the Renner-Teller interaction. It also allows the effects of large amplitude motion on the rotational structure to be calculated, including the switchover from bent to linear behaviour. Author Institution: Department of Physics, SUPA, John Anderson Building, University of; Strathclyde, 107 Rottenrow, Glasgow G4 0NG, Scotland, UK; LAC, 1 Laboratoire Aime Cotton du CNRS, Universite de Paris-Sud, 91405 Orsay, France; GSMA, UMR CNRS 6089, Universite de Reims Champagne-Ardenne,B.P. 1039, 51687 Reims Cedex 2, France

2012-01-01T00:00:00Z Duxbury, G. Jungen, Ch. Alijah, A. Hefferlin, R. Clark, B. Tatum, J. http://hdl.handle.net/1811/52581 2012-07-09T20:33:41Z 2012-01-01T00:00:00Z

COMPARISON OF COMPUTED CONDON LOCI WITH FRANCK-CONDON FACTORS IN DESLANDRES TABLES OF MOLECULAR BAND SYSTEMS Hefferlin, R.; Clark, B.; Tatum, J. The literature often shows a Condon parabola not quite tracking the Franck-Condon factors for the strongest bands in the Deslandres table for a diatomic molecular band system ; often the parabola appears to have been hand-drawn. We have calculated Condon loci, assuming originally that the lower and upper electronic potentials are simple harmonic potentials, and assuming now that they are Morse potentials. In the harmonic case the Condon loci are parabolas. These calculations are for small vibrational quantum numbers, where the Morse loci also begin as parabolas. We will present these loci for representative molecular band systems and discuss the extent to which the loci track the strongest Franck-Condon factors. In the event that neither does, calculations for arbitrary potentials are available. The importance of this study is that we have previously calculated the latera recta and the symmetry-axis angles of the harmonic oscillator parabolas in Deslandres tables appropriate to molecules in several isoelectronic sequences. We have found that the angle increases along the sequence until the species one proton-shift away from "rare-gas" molecules, such as LiNe, is reached. This phenomenon is a suggestion that diatomic molecules are periodic with respect to each of their two atoms. Author Institution: Southern Adventist University, Collegedale, TN 37315; University of Victoria, Victoria, BC V8W 2Y2, Canada

2012-01-01T00:00:00Z Hefferlin, R. Clark, B. Tatum, J. Groner, P. Albert, S. Quack, M. http://hdl.handle.net/1811/52580 2012-07-09T20:33:40Z 2012-01-01T00:00:00Z

USING PROGRAM ERHAM TO ANALYZE HIGH-RESOLUTION INFRARED SPECTRA OF MOLECULES WITH INTERNAL ROTORS Groner, P.; Albert, S.; Quack, M. The effective rotational Hamiltonian for molecules with one or two periodic large-amplitude motions 107, 4483 (1997).} implemented in program ERHAM has been adapted to enable prediction and least-squares fits of rotationally resolved lines in vibration-rotation spectra in the infrared region. The modified program is currently applied to assign the band of methyl formate at 925 cm$^{-1}$ that has been measured at ETH in Zurich on the IFS125 Bruker prototype ZP 2001 FTIR spectrometer 8, 1271 (2007)} at a resolution of 0.001 cm$^{-1}$. An external glass cell with an optical path length of 3 m contained the sample, and 150 interferograms were co-added. Right now it looks as if the splitting into $A$ and $E$ components were a little too small to be resolved sufficiently for positive identification. Author Institution: Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110-2499; Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland

2012-01-01T00:00:00Z Groner, P. Albert, S. Quack, M. Catikkas, Berna http://hdl.handle.net/1811/52582 2012-07-09T20:47:20Z 2012-01-01T00:00:00Z

VIBRATIONAL SPECTRA OF THE MLCl${_2}$ COMPLEX FROM THEORETICAL CALCULATIONS Catikkas, Berna The geometric and vibrational parameters (harmonic and anharmonic frequencies) of the MLCl${_2}$ [M= Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg; L= Ethylenediamine (en)] donor-acceptor complexes have been studied by using HF and MPW1PW91+iop(3/76=00572004280)/gen methods. Binding, reorganization, atomization, HOMO-LUMO and ionization potential energies have also been calculated with the same method. SQM calculations have been performed by using anharmonic frequencies and experimental data. The obtained results were found to be in good agreement with the corresponding experimental findings. Author Institution: Department of Physics, Mustafa Kemal University, Hatay, Turkey, 31034 (email to B.C.: berna@mku.edu.tr)

2012-01-01T00:00:00Z Catikkas, Berna Lodi, L. Tennyson, J. http://hdl.handle.net/1811/52577 2012-12-29T08:08:07Z 2012-01-01T00:00:00Z

TOWARDS PERFECT WATER LINE INTENSITIES Lodi, L.; Tennyson, J. Over the last ten years the increased availability of computational resources and the steady refinement of theoretical methods have permitted more and more accurate first principle calculations of water-vapor spectra as exemplified, e.g., by the very successful BT2 line list, 1087-1094 (2006).}. There are two requirements for computing accurate line lists from first principles: a high-accuracy potential energy surface (PES), affecting both line positions and intensities, a reliable dipole moment surface (DMS), affecting line intensities. It is also very useful to several application to give reasonable uncertainty bars for computed quantities, an aspect which traditionally has received little attention. We report here recent progress leading to very accurate room-temperature linelists covering the range 0.05--20~000~cm$^{-1}$, complete with uncertainty bars, for the H$_2^{18}$O and H$_2^{17}$O water isotopologues. Line intensities were produced using a recent DMS produced by our group, 034113 (2011).} which is capable of giving line intensites accurate to 1\% for most medium and strong transitions. Line positions are based if possible on the experimentally derived energy levels recently produced by a IUPAC task group, 573-96 (2009).} and have a typical accuracy of 0.0002~cm$^{-1}$; when experimentally derived energy levels are unavailable calculated line position are provided, with an accuracy of the order of 0.2~cm$^{-1}$. An extension to the main isotopologue H$_2^{16}$O is currently underway. Author Institution: Department of Physics and Astronomy, University College London, London WC1E 6BT, UK

2012-01-01T00:00:00Z Lodi, L. Tennyson, J. Huang, Xinchuan Schwenke, David W. Lee, Timothy J. Sung, Keeyoon Brown, Linda R. Tashkun, Sergey A. http://hdl.handle.net/1811/52579 2012-07-09T20:33:39Z 2012-01-01T00:00:00Z

THEORETICAL NH${_3}$ SPECTRA IN 5800-7000 CM$^{-1}$ REGION AND CO${_2}$ IR INTENSITY: UPDATES Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J.; Sung, Keeyoon; Brown, Linda R.; Tashkun, Sergey A. Recently we have successfully applied the "Best Theory + High-resolution Experimental Data" strategy to NH${_3}$ nderline{\textbf129}, 214304 (2008); \textit{J. Chem. Phys.} nderline{\textbf134}, 044320/044321 (2011).} and CO${_2}$. nderline{\textbf136}, ,submitted (2012).} The essential strategy is to refine a high quality, purely ab initio potential energy surface (PES) with reliable high resolution experimental data, so the IR line lists computed on the refined PES and dipole moment surface (DMS) can go beyond simple data reproduction. The goal is to make reliable predictions for higher J/K/energy rovibrational transitions with similar accuracies, i.e. 0.01-0.03 cm$^{-1}$. The reliability and accuracy of data included in the refinement largely determines the quality of predictions and the ultimate merit of our work. With recent $^{14}$NH${_3}$ experiments in 5800 - 7000 cm$^{-1}$, the effective coverage (with 0.01-0.03 cm$^{-1}$ accuracy) of our NH${_3}$ PES has extended to this complex spectral region. Excellent agreement between current experiment analysis and our primitive HSL-3 PES refinement will be presented, and source of discrepancies will be discussed. The synergy between the experiments and theory is of great value. For CO${_2}$, we have updated the theoretical IR intensity of the $^{12}$C$^{16}$O${_2}$ line list with a more reliable DMS, then carried out very detailed comparisons with both pure experimental data and HITRAN/CDSD models. Results suggest that our line lists should be useful for the astronomical or earth-based detection of CO${_2}$ isotopologues. Author Institution: SETI Institute, 189 Bernardo Ave, Suite 100, Mountain View, CA, 94043; MS T27B-1, NASA Ames Research Center, Moffett Field, CA, 94035; MS 245-1, NASA Ames Research Center, Moffett Field, CA, 94035; Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109; Laboratory of Theoretical Spectroscopy, V.E. Zuev Institute of Atmospheric Optics, SB, Russian Academy of Science, 634055, Tomsk, Russia

2012-01-01T00:00:00Z Huang, Xinchuan Schwenke, David W. Lee, Timothy J. Sung, Keeyoon Brown, Linda R. Tashkun, Sergey A. Thorwirth, S. Krieg, J. Keppeler, I. Lutter, V. Schlemmer, S. Giesen, T. F. Harding, M. E. Vazquez, J. http://hdl.handle.net/1811/52578 2012-07-09T20:33:38Z 2012-01-01T00:00:00Z

HIGH-RESOLUTION INFRARED SPECTROSCOPY OF THE $(1,0,1)-(0,0,0)$ BAND OF C$_3$ Thorwirth, S.; Krieg, J.; Keppeler, I.; Lutter, V.; Schlemmer, S.; Giesen, T. F.; Harding, M. E.; Vazquez, J. Using the carbon cluster experiment at Cologne in combination with a home-made optical parametric oscillator operating at three microns, the $(1,0,1)-(0,0,0)$ combination band of the C$_3$ cluster has been investigated around 3260\,\wn . In addition, the associated $(1,1,1)-(0,1,0)$ hot band has been observed. Using sample rods enriched in $^{13}$C, the $(1,0,1)-(0,0,0)$ band was also studied for the two isotopologs $^{13}$CCC and C$^{13}$CC. The experimental molecular parameters obtained compare very favorably with results from coupled-cluster calculations. Author Institution: I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany; Karlsruher Institut fur Technologie, Institut fur; Nanotechnologie, 76021 Karlsruhe, Germany; Center for Theoretical; Chemistry, Department of Chemistry and Biochemistry, The University of; Texas at Austin, Austin, Texas 78712, U.S.A

2012-01-01T00:00:00Z Thorwirth, S. Krieg, J. Keppeler, I. Lutter, V. Schlemmer, S. Giesen, T. F. Harding, M. E. Vazquez, J. Down, Michael J. Tennyson, Jonathan Orphal, Johannes Chelin, Pascale Ruth, Albert A. http://hdl.handle.net/1811/52576 2012-12-29T08:08:19Z 2012-01-01T00:00:00Z

ANALYSIS OF AN $^{18}$O AND D ENHANCED FT-IBBCEAS WATER SPECTRUM: NEW ASSIGNMENTS FOR HD$^{18}$O, HD$^{16}$O, D$_2$$^{18}$O AND D$_2$$^{16}$O IN THE NEAR-INFRARED REGION (6000-7000 cm$^{-1}$). Down, Michael J.; Tennyson, Jonathan; Orphal, Johannes; Chelin, Pascale; Ruth, Albert A. An experimental infrared spectrum recorded using isotopically enriched water in the 6000-7000~cm$^{-1}$ region with a spectral resolution of 0.02~cm$^{-1}$ is analysed and assigned. The spectrum employs a combination of Fourier-transform (FT) spectroscopy and incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) . Application of FT-IBBCEAS to a sample mixture of 8.0 mbar of D$_{2}$O and 12.4 mbar of pure H$_{2}$$^{18}$O in the optical cavity resulted in the observation of a large number of new absorption features in the spectrum, notably due to the rare HD$^{18}$O isotope of water. This was possible due to the superior absorption sensitivity of FT-IBB-CEAS compared to other techniques previously employed in this region %, combined with the prescence of D$_{2}$$^{16}$O in the sample. The assignment procedure is based on the use of known transition frequencies for H$_{2}$$^{16}$O and H$_{2}$$^{18}$O, existing variational line lists for HD$^{16}$O % and D$_{2}$$^{16}$O %, and newly calculated variational line lists for HD$^{18}$O and D$_{2}$$^{18}$O, with a uniform intensity threshold applied. The main absorption comes from HD$^{16}$O and HD$^{18}$O, for which there are few previous assignments in the region. %$^,$. The following new spectral features were identified. D$_{2}$$^{16}$O: 265 (all labelled); D$_{2}$$^{18}$O: 194 (all lower levels labelled); HD$^{16}$O: 213 (all labelled); HD$^{18}$O: 743 (all lower and 612 upper levels labelled). In all 3226 of the 4768 lines observed in the spectrum are assigned, resulting in a significant number of newly determined energy levels. The analysis demonstrates both the usefulness of this experimental approach for spectroscopic investigations of isotopic or dangerous samples, and the validity of the new variational line lists. Author Institution: Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK; Karlsruher Institut fur Technologie, IMK-ASF, Postfach 36 40, 76021 Karlsruhe, Germany; Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), Universite de Paris-Est, CNRS UMR 7583, Creteil, France; Physics Department and Environmental Research Institute, University College Cork, Cork, Ireland

2012-01-01T00:00:00Z Down, Michael J. Tennyson, Jonathan Orphal, Johannes Chelin, Pascale Ruth, Albert A. Gord, Joseph R. Roy, Sukesh Hsu, Paul S. Jiang, Naibo Kulatilaka, Waruna D. Stauffer, Hans U. Gord, James R. http://hdl.handle.net/1811/52575 2012-12-29T08:08:11Z 2012-01-01T00:00:00Z

DIRECT MEASUREMENTS OF COLLISIONALLY BROADENED (CO$_{2}$-CO$_{2}$) S-BRANCH RAMAN COHERENCE LIFETIMES OF CO$_{2}$ Gord, Joseph R.; Roy, Sukesh; Hsu, Paul S.; Jiang, Naibo; Kulatilaka, Waruna D.; Stauffer, Hans U.; Gord, James R. We report direct measurement of S-branch Raman coherence lifetimes of CO$_{2}$ due to CO$_{2}$-CO$_{2}$ collisions by employing picosecond time-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy. A custom-built, high-peak-power, nearly transform-limited ps laser system offers an ideal combination of frequency and temporal resolution for such measurements. The rotational S-branch transitions of CO$_{2}$ ground state [0,0$^{0}$,0] with rotational quantum number J$=0-52$ were simultaneously excited by using a broadband ($\sim$3-nm) laser pulse with a full-width-half-maximum (FWHM) of $\sim$100 ps. The coherence lifetimes of self-broadened CO$_{2}$ for a pressure range of 0.05-1.5 bar were directly measured by probing the rotational coherence with a nearly transform-limited, 80-ps-long laser pulse. The measured linewidth of J=6 and J=50 transitions are found to be $\sim$0.106$\pm$0.0002 and $\sim$0.070$\pm$0.0002, respectively. As expected, the energy-transfer from high J levels has a significantly longer coherence lifetime because of the inertia associated with higher angular momentum. These measurements are very significant for performing accurate thermometry or CO$_{2}$ concentration measurements in gas-phase reacting flows. Author Institution: Department of Chemistry, Purdue University, West Lafayette, IN 47907; Spectral Energies, LLC, 5100 Springfield Street, Suite 301, Dayton, OH 45431; Air Force Research Laboratory, Propulsion Directorate, Wright-Patterson AFB, OH 45433

2012-01-01T00:00:00Z Gord, Joseph R. Roy, Sukesh Hsu, Paul S. Jiang, Naibo Kulatilaka, Waruna D. Stauffer, Hans U. Gord, James R. Mills, Andrew A. Jiang, Jie Hartl, Ingmar Fermann, Martin Gatti, Davide Marangoni, Marco http://hdl.handle.net/1811/52574 2012-07-09T20:33:20Z 2012-01-01T00:00:00Z

QCL SPECTROSCOPY AT 9 $\mu$M CALIBRATED WITH A HIGH-POWER THULIUM-BASED FREQUENCY COMB Mills, Andrew A.; Jiang, Jie; Hartl, Ingmar; Fermann, Martin; Gatti, Davide; Marangoni, Marco Optical frequency comb synthesizers (OFCS) comprised of mode-locked femtosecond lasers can be stabilized with Hertz-level accuracy and used in combination with cw lasers for high resolution spectroscopy. As currently established OFCS technologies are confined to the near-IR, mid-IR spectroscopy requires either down-conversion of near-IR combs or up-conversion of the probing laser. Due to the near-IR absorption edge of the nonlinear crystals with extended mid-IR transparency, the conversion efficiency of nonlinear processes increases with the wavelength of the interacting fields. A more straightforward and efficient link between comb and probing laser is thus expected to be obtained by increasing the wavelength of the comb synthesizer. In this work, the use of a novel, powerful Thulium-based OFCS~nderline{\textbf{PDB\_1}}, 2001} with emission wavelengths near 2 $\mu$m is shown to be an excellent candidate to obtain absolute frequency calibration of quantum cascade lasers (QCL) operating at wavelengths as long as 9 $\mu$m. Specifically, by combining the frequencies of a 9 $\mu$m QCL with the high power 2 $\mu$m comb in a AgGaSe$_2$ crystal, SFG light is created near 1.6 $\mu$m. A portion of the 2 $\mu$m comb is non-linearly shifted to 1.6 $\mu$m. As the carrier envelope offset frequency ($f_{ceo}$) is the same for the SFG radiation and the shifted comb at 1.6 $\mu$m, heterodyning the two signals produces a beat signal independent of $f_{ceo}$, eliminating the need for an octave spanning comb and f-2f interferometer. We report on the development of this instrument, and the absolute line transitions of NH$_3$ at 9 $\mu$m, enabled by rapid scanning of the repetition rate of the comb enabled to increase the signal-to-noise ratio.~nderline{\textbf{19}}, 17520 2011} %%The first OFCS referencing of a QCL was performed at 4.4 $\mu$m via sum-frequency generation process with a Nd:YAG laser.~nderline{\textbf{32}}, 988 2007} The SFG radiation was heterodyned with a external-cavity diode laser (ECDL), where both the YAG and ECDL were locked to the OFCS. The active stabilization of $f_{ceo}$ requires an octave spanning comb and a f-2f interferometer. Author Institution: IMRA America, Ann Arbor, MI; Campus Point, Dipartimento di Fisica del Politecnico di Milano, Milano, Italy

2012-01-01T00:00:00Z Mills, Andrew A. Jiang, Jie Hartl, Ingmar Fermann, Martin Gatti, Davide Marangoni, Marco Holland, Daniel B. Blake, Geoffrey A. http://hdl.handle.net/1811/52573 2012-07-09T20:33:19Z 2012-01-01T00:00:00Z

DEVELOPMENT OF A HIGHER RESOLUTION TERAHERTZ TIME-DOMAIN SPECTROMETER Holland, Daniel B.; Blake, Geoffrey A. We report on our development of a terahertz (THz) time-domain spectrometer employing asynchronous optical sampling (ASOPS) between two commercial Ti:Sapphire lasers operating with a repetition rate of approximately 80 MHz. THz time-domain spectrometers typically achieve control of sampling time delay via the use of mechanical delay lines, yielding a practically feasible resolution limit of several GHz. There are commercially available THz time-domain spectrometers employing ASOPS with GHz repetition rate lasers; they achieve 1 GHz resolution. The use of our lower repetition rate lasers, while introducing technical challenges, offers a theoretical resolution limit of 80 MHz, an important benefit for our primary application of collecting THz spectra in support of astronomy in the far-infrared. Technical data on instrument design and performance as well as initial spectra are to be presented. Author Institution: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125 (email to D.B.H.: holland@caltech.edu); Division of Geological and Planetary Sciences, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125

2012-01-01T00:00:00Z Holland, Daniel B. Blake, Geoffrey A. Henderson, A. http://hdl.handle.net/1811/52572 2012-12-29T08:04:45Z 2012-01-01T00:00:00Z

A MULTI-WATT SINGLE FREQUENCY CW OPO SYSTEM TUNABLE FROM 600NM TO 4600NM Henderson, A. The output wavelength range of commercial CW OPOs has been dramatically extended to reach both further into the mid-infrared and into the visible/ near-infrared, providing a tuning range from 600nm to 4600nm. Specific examples of new capabilities are provided below: \vspace{1em} (1) Extension of the mid-infrared wavelength coverage to 4630nm by annealing of the PPLN crystal to reduce OH absorption (2) Generation of 3Watts of orange radiation tunable 604nm to 616nm by intra-cavity sum frequency generation of OPO pump and signal (3) Generation of over 100mW near-IR radiation tunable 1240nm to 1500nm by extra-cavity second harmonic generation of OPO idler \vspace{1em} In each case, the same robust 1064nm fiber laser pump source may be interchanged between these OPO modules to access specific wavelength ranges. In all of the examples above, the wide (100GHz) mode-hop-free tunability of the source is retained, making the output ideal for high resolution spectroscopy. The high power, narrow (sub-MHz) linewidth and excellent beam quality of the OPO output make it an ideal pump source for secondary nonlinear processes to reach further into the visible/UV and mid-infrared / Terahertz while providing spectroscopic measurement capability. Author Institution: LOCKHEED MARTIN ACULIGHT, 22121 20th Avenue SE, Bothell, WA 98021

2012-01-01T00:00:00Z Henderson, A. Chandler, David W. Strecker, Kevin E. http://hdl.handle.net/1811/52571 2012-12-29T08:04:48Z 2012-01-01T00:00:00Z

DUAL ETALON FREQUENCY COMB (DEFCOM) SPECTROSCOPY Chandler, David W.; Strecker, Kevin E. A new spectrometer based on an interferogram produced by the output of two separate confocal etalons is described and first experiments will be described. This spectrometer has the resolution of the Free Spectral Range (FSR) of the etalons on a single laser shot over the bandwidth of the light source that that is used to excite the etalons. With signal averaging and scanning of the etalon mirror the resolution can be that of the "ring-down" time of the etalons. By placing the sample of interest within one of the etalons one obtains the sensitivity of cavity ring down spectroscopy while performing Cavity Ring Down (CRD) spectroscopy over the entire bandwidth of the laser source used to excite the etalon. First data on measurements of overtone absorptions of water and weak electronic gamma-band absorption of oxygen will be presented. Work supported by DOE Basic Energy Sciences.; Author Institution: Sandia National Laboratory, Livermore, CA 94550

2012-01-01T00:00:00Z Chandler, David W. Strecker, Kevin E. Iwakuni, K. Okubo, S. Nakayama, H. Sasada, H. Inaba, H. http://hdl.handle.net/1811/52570 2012-12-29T08:08:17Z 2012-01-01T00:00:00Z

OPTICAL FREQUENCY COMB REFERNCED SUB-DOPPLER RESOLUTION DIFFERENCE-FREQUENCY-GENERATION INFRARED SPECTROMETER Iwakuni, K.; Okubo, S.; Nakayama, H.; Sasada, H.; Inaba, H. We have determined absolute frequencies of 56 transition of the $\nu_3$ band of $^{12}$CH$_4$ and $^{13}$CH$_4$ with at a typical uncertainty level of 2 kHz. While the frequency of the difference-frequency-generation (DFG) source is stabilized to the Lamb dip of the methane transition, the frequencies of the pump and signal source are measured with a 1.5-$\mu$m optical frequency comb (OFC). The determined value is consistent with the International Committee for Weight and Measures recommendation within the uncertainty. We have also developed OFC-referenced frequency sweep, which allow us to accumulate spectral data for long time without any frequency drift and to determine the frequency of the transition which are too weak to use the frequency reference for the frequency stabilization. Author Institution: Department of Phisics, Faculty of Science and Technology, Keio University, Yokohama, Japan; National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

2012-01-01T00:00:00Z Iwakuni, K. Okubo, S. Nakayama, H. Sasada, H. Inaba, H. Okubo, S. Nakayama, H. Iwakuni, K. Sasada, H. Inaba, H. http://hdl.handle.net/1811/52569 2012-12-29T08:08:14Z 2012-01-01T00:00:00Z

SUB-DOPPLER RESOLUTION DIFFERENCE-FREQUENCY-GENERATION INFRARED SPECTROMETER WITH HIGH SENSITIVITY AND WIDE TUNABILITY Okubo, S.; Nakayama, H.; Iwakuni, K.; Sasada, H.; Inaba, H. We made a 3.4-$\mu$m spectrometer that consists of a 1.06-$\mu$m Nd:YAG laser as a pump source, a 1.55-$\mu$m extended-cavity laser diode (ECLD) as a signal source, and a waveguide-type periodically-poled lithium niobate (PPLN) with a difference-frequency-generation efficiency of 10 $\%$/W. The linewidth of the ECLD is reduced less than 50 kHz by stabilizing the 3.4-$\mu$m frequency to one of the modes of a Fabry-Perot cavity, which is also employed as an absorption cell to increase the effective absorption length and to enhance the optical field strength at the antinodes. The spectrometer conjunction with wavelength modulation spectroscopy allows us to record 300 kHz wide Lamb dips of the $\nu_3$ band of $^{12}$CH$_4$ and $^{13}$CH$_4$ from 88.2 to 90.5 THz. The tunable range currently limited by the phase matching condition of the PPLN can be extended from 83 to 94 THz. Author Institution: Department of Physics, Faculty of Science and Technology, Keio University, Yokohama, Japan; National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

2012-01-01T00:00:00Z Okubo, S. Nakayama, H. Iwakuni, K. Sasada, H. Inaba, H. Huang, Xinchuan Schwenke, David W. Lee, Timothy J. http://hdl.handle.net/1811/52568 2012-07-09T20:33:03Z 2012-01-01T00:00:00Z

TOWARDS AN ACCURATE INFRARED LINELIST FOR SO${_2}$ Huang, Xinchuan; Schwenke, David W.; Lee, Timothy J. The "Best Theory + High-resolution Expt Data" strategy now extends from NH${_3}$, CO${_2}$ to SO${_2}$ which is considered a "weed" in åÊhigh resolution astronomical data analysis (such as for Herschel, SOFIA, and JWST).åÊ Refining a high quality ab initio potential energy surface (PES) with selected HITRAN data, we have made significant progress toward an accurate IR line list for SO${_2}$. Similar to the situation for CO${_2}$, we have achieved 0.01-0.02 cm$^{-1}$ accuracy for reliable line positions. Outliers in existing HITRAN models have been identified. Compared to CO${_2}$, the SO${_2}$ rovibrational energy levels are more difficult to converge. A pure, experimentally measured dataset (instead of HITRAN models) would greatly enhance the reliabilty of higher J/K and higher energy levels computed on the refined PES. An initial IR line list has been generated to test an ab initio dipole moment surface (DMS). Limitations, deficiencies, and future developments for both line positions and IR intensities will be discussed. Author Institution: SETI Institute, 189 Bernardo Ave, Suite #100, Mountain View, CA, 94043; MS T27B-1, NASA Ames Research Center, Moffett Field, CA, 94035; MS 245-1, NASA Ames Research Center, Moffett Field, CA, 94035

2012-01-01T00:00:00Z Huang, Xinchuan Schwenke, David W. Lee, Timothy J. White, Allen R. Yalamanchili, Bharat http://hdl.handle.net/1811/52567 2012-12-29T08:08:09Z 2012-01-01T00:00:00Z

TIME RESOLVED FTIR ANALYSIS OF COMBUSTION OF AN ETHANOL/ISOPROPANOL MIXTURE IN A COMMERICIAL INTERNAL COMBUSTION ENGINE White, Allen R.; Yalamanchili, Bharat In order to measure infrared (IR) emission from combustion in an internal combustion engine, a small commercial spark ignition engine was modified with a ZnSe optical access window. This modification allows for transmission of IR radiation for time-resolved spectroscopic measurements by a Fourier-Transform IR (FTIR)spectrometer. By using a Step-scan equipped Fourier transform spectrometer, temporally resolved infrared spectral data were acquired and compared for combustion in the modified engine. These measurements provide insight into the energy transfer vectors during the combustion process and also provides an in situ measurement of the progress of combustion (via CO2 production). Measurements were performed using an ethanol and isopropanol mixture to provide additional IR sources to trace during the combustion process. Author Institution: Department of Mechanical Engineering, Rose-Hulman Institute of Technology, 5500 Wabash Ave., Terre Haute, IN 47803

2012-01-01T00:00:00Z White, Allen R. Yalamanchili, Bharat Engel, Gregory S. http://hdl.handle.net/1811/52566 2012-07-09T20:32:56Z 2012-01-01T00:00:00Z

IMAGING EXCITED STATE DYNAMICS WITH 2D ELECTRONIC SPECTROSCOPY Engel, Gregory S. Excited states in the condensed phase have extremely high chemical potentials making them highly reactive and difficult to control. Yet in biology, excited state dynamics operate with exquisite precision driving solar light harvesting in photosynthetic complexes though excitonic transport and photochemistry through non-radiative relaxation to photochemical products. Optimized by evolution, these biological systems display manifestly quantum mechanical behaviors including coherent energy transfer, steering wavepacket trajectories through conical intersections and protection of long-lived quantum coherence. To image the underlying excited state dynamics, we have developed a new spectroscopic method allowing us to capture excitonic structure in real time. Through this method and other ultrafast multidimensional spectroscopies, we have captured coherent dynamics within photosynthetic antenna complexes. The data not only reveal how biological systems operate, but these same spectral signatures can be exploited to create new spectroscopic tools to elucidate the underlying Hamiltonian. New data on the role of the protein in photosynthetic systems indicates that the chromophores mix strongly with some bath modes within the system. The implications of this mixing for excitonic transport will be discussed along with prospects for transferring underlying design principles to synthetic systems. Author Institution: Department of Chemistry, The University of Chicago, Chicago USA

2012-01-01T00:00:00Z Engel, Gregory S. Mullin, Amy S. Toro, Carlos Echibiri, Geraldine Liu, Qingnan http://hdl.handle.net/1811/52565 2012-12-29T08:08:24Z 2012-01-01T00:00:00Z

SPECTROSCOPY OF MOLECULES IN EXTREME ROTATIONAL STATES USING AN OPTICAL CENTRIFUGE Mullin, Amy S.; Toro, Carlos; Echibiri, Geraldine; Liu, Qingnan Our lab has developed a high-power optical centrifuge that is capable of trapping and spinning large number densities of molecules into extreme rotational states. By coupling this device with high resolution transient IR absorption spectroscopy, we measure the time-resolved behavior and energy profiles of individual ro-vibrational states of molecules in very high rotational states. Recent results will be discussed on the spectroscopy of new rotational states, collisional dynamics in the optical centrifuge, spatially-dependent energy profiles and possibilities for new chemistry induced by centrifugal forces. Author Institution: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742

2012-01-01T00:00:00Z Mullin, Amy S. Toro, Carlos Echibiri, Geraldine Liu, Qingnan Lester, Marsha I. http://hdl.handle.net/1811/52564 2012-12-29T08:08:20Z 2012-01-01T00:00:00Z

A NEW SPECTROSCOPIC WINDOW ON HYDROXYL RADICALS AND THEIR ASSOCIATION REACTIONS OF SIGNIFICANCE IN THE ATMOSPHERE Lester, Marsha I. The weakly bound hydrogen trioxy radical (HOOO), produced in the association reaction of the hydroxyl radical (OH) with molecular oxygen (O$_2$), has been postulated to play an important role in atmospherically relevant reactions. Experimental studies in this laboratory have utilized infrared action spectroscopy to probe the structure, vibrational frequencies, and stability of this weakly bound species. {\bf 42}, 419-427 (2009).} Recent experimental and theoretical results on HOOO will be presented, and used in assessing its significance in the atmosphere. {\bf 134}, 044304 (2011).} Most studies of the hydroxyl radical and its association products utilize laser-induced fluorescence on the well-characterized OH A$^2\Sigma^+$ - X$^2\Pi$ band system for detection. This laboratory has recently demonstrated a new photoionization scheme combining initial UV excitation on the A$^2\Sigma^+$ - X$^2\Pi$ band system with subsequent fixed-frequency VUV ionization via autoionizing Rydberg states. {\bf134}, 241102 (2011).} The photoionization mechanism as well as the applicability of this quantum state-selective photoionization scheme will be presented. This research was supported by the National Science Foundation and the Office of Basic Science of the Department of Energy.; Author Institution: Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323

2012-01-01T00:00:00Z Lester, Marsha I. Ramabhadran, Raghunath O. Mayhall, Nicholas J. Becher, Edwin L., III Chowdhury, Arefin Raghavachari(s), Krishnan http://hdl.handle.net/1811/52563 2012-12-29T08:08:18Z 2012-01-01T00:00:00Z

ELUCIDATION OF PROTON-ASSISTED FLUXIONALITY IN TRANSITION-METAL OXIDE CLUSTERS Ramabhadran, Raghunath O.; Mayhall, Nicholas J.; Becher, Edwin L., III; Chowdhury, Arefin; Raghavachari(s), Krishnan The phenomenon of fluxionality in the reactions of transition-metal oxide clusters provides many opportunities in various industrial and catalytic processes. We present an electronic structure investigation of the fluxionality pathways when anionic W3O6- and Mo3O6- clusters react with three small molecules - water, ammonia and hydrogen sulfide. The presentation features a detailed understanding of (a) how the fluxionality pathway occurs and (b) the various factors that affect the fluxionality pathway - such as the metal, different spin-states and the nature of the non-metal in the reacting small molecule. Author Institution: Department of chemistry, Indiana University, Bloomington, IN-47405

2012-01-01T00:00:00Z Ramabhadran, Raghunath O. Mayhall, Nicholas J. Becher, Edwin L., III Chowdhury, Arefin Raghavachari(s), Krishnan Gardner, Adrian M. Plowright, Richard J. Graneek, Jack Wright, Timothy G. Breckenridge, W. H. http://hdl.handle.net/1811/52562 2012-12-29T08:08:16Z 2012-01-01T00:00:00Z

THEORETICAL INVESTIGATION OF THE M$^{+}$-RG$_{2}$ (M = ALKALINE EARTH METAL; RG = RARE GAS) COMPLEXES Gardner, Adrian M.; Plowright, Richard J.; Graneek, Jack; Wright, Timothy G.; Breckenridge, W. H. Metal cation rare gas complexes provide an expectedly simple system with which to investigate intermolecular interactions. Despite this, we have previously found the M$^{+}$-RG (M = alkaline earth metal) complexes to very complicated systems, with the complexes of the heavier rare gases displaying surprisingly large degrees of chemical character., \textbf{2000}, \textit{114}, 7631.}$^,$, \textbf{2010}, \textit{132}, 054302.}$^,$, \textbf{2009}, \textit{130}, 194305.} Here we extend these studies by examining the nature of these interactions with increasing degrees of solvation through investigating the M$^{+}$-RG$_2$ complexes using high level \textit{ab initio} techniques. Intriguing trends in the geometries and dissociation energies of these complexes have been observed and are rationalized. Author Institution: School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, USA

2012-01-01T00:00:00Z Gardner, Adrian M. Plowright, Richard J. Graneek, Jack Wright, Timothy G. Breckenridge, W. H.