Abstracts of OSU International Symposium on Molecular Spectroscopy 2000-2009
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This collection contains the abstracts of the OSU International Symposium on Molecular Spectroscopy from 2000-2009 (and complete presentations from authors who have so authorized for years 2005-2009).
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Item HIGH RESOLUTION ELECTRONIC SPECTROSCOPY OF THE ARGON VAN DER WAALS COMPLEXES OF 1, 2, 3, 6, 7, 8-HEXAHYDROPYRENE IN THE GAS PHASE.(Ohio State University, 2009) Morgan, Philip J.; Fleisher, Adam J.; Roscioli, Joseph R.; Pratt, David W.The study of van der Waals complexes provides structural and dynamical information about the weak chemical forces that exist between aromatic molecules and rare gas atoms. In this report, we describe the rotationally resolved fluorescence excitation spectra of the S$_1$$\leftarrow$S$_0$ origin bands of the single argon atom complexes of 1, 2, 3, 6, 7, 8-hexahydropyrene. Analysis of the spectra provides information about the geometries of both conformers of the bare molecule and their argon complexes in both electronic states. The equilibrium positions of the argon atom in both conformers will be discussed.Item HIGH RESOLUTION INVESTIGATION OF SILACYCLOBUTANE USING FTMW AND SYNCHROTRON BASED FTIR SPECTROSCOPY(Ohio State University, 2009) Dijk, Cody Van; Nest, Samantha Van; Chen, Ziqiu; Wijngaarden, Jennifer VanThe rotational spectrum of silacyclobutane (c-C${_3}$H${_8}$Si) has been measured between 8 and 24 GHz using Fourier transform microwave spectroscopy. Although the microwave spectrum was previously reported \underline{\textbf{54}} (4979), 1971.}, the current study is the first observation of tunneling splitting in the ground state due to ring puckering. The observed transitions within each tunneling state obey \textit{a-}type selection rules and \textit{c-}type transitions that connect the inversion states have also been observed. The rotational constants determined were used to model the rotational structure of several vibrational bands of silacyclobutane including the weak ring puckering mode at 157 cm$^{-1}$. The far infared spectrum of silacyclobutane was recorded using the far infrared beamline at the Canadian Light Source and includes multiple tunneling doubled bands. The ongoing analysis of the incredibly rich vibrational spectrum of silacyclobutane will be discussed.Item HELIUM DROPLETS AS NANO-CRYOSTATS FOR MOLECULAR SPECTROSCOPY: AGGREGATION, STATE SELECTION AND ELECTRON SPIN RESONANCE(Ohio State University, 2009) Ernst, Wolfgang E.Droplets of about $10^{4}$ helium atoms generated in a supersonic expansion, represent a nanometer-sized superfluid medium of 0.4 K temperature and can be doped with one or several atoms or molecules that may form complexes in this cold environment. Using two-laser excitation schemes, we were able to identify the alkali trimers K$_3$, Rb$_3$, K$_2$Rb and KRb$_2$ in their lowest quartet states formed on helium droplets loaded with potassium and rubidium atoms and assign several excited states that underlie both Jahn-Teller and spin-orbit coupling. As helium provides a gentle and only weakly perturbing matrix, it appeared desirable to look for ways to measure fine and hyperfine structure directly in the microwave or radiofrequency regime. In preparation for experiments involving optical detection of electron spin transitions in cold molecules, we studied the electronic spin relaxation in alkali atoms and molecules that reside on the surface of a droplet. Measurements of the circular dichroism in the presence of a magnetic field showed that the populations of Zeeman sublevels in alkali atoms are not thermalized, while for dimers and trimers a temperature of 0.4 K was found, implicitly providing a first determination of the droplet s surface temperature. Optical detection of spin resonance is achieved in an optical pump-probe experiment with the electron spin transition induced in a microwave cavity in a magnetic field between the pump and probe regions. With the pump laser depleting a particular spin state by desorption of the species from the droplet beam or by optical pumping, the probe laser detects the successful spin flip induced by the microwave field. Examples will be presented showing up to 50 Rabi cycles of an electron spin transition on an alkali doped helium droplet during the flight time of 57 $\mu$s through the cavity.Item INFRARED VACUUM ULTRAVIOLET SPECTROSCOPY OF ALLYL RADICAL(Ohio State University, 2009) Reed, B.; Lam, C. S.; Xing, X.; Lau, K. C.; Ng, C. Y.; Zhang, X.; Vasiliou, A.; Ellison, G. B.An infrared (IR)-vacuum ultraviolet (VUV) double resonance experiment on the allyl (CH$_2$CHCH$_2$) radical will be described. The pulsed field ionization-photoelectron (PFI-PE) spectrum of the allyl (CH$_2$CHCH$_2$) radical has already been obtained and used to determine the accurate ionization energy of 65 584.6 +/- 2.0 cm$^{-1}$ (8.131 46 ±0.000 25 eV). Next, building on previous work which identified IR resonances at 3113.98 and 3110.59 cm$^{-1}$, we anticipate the first IR-VUV double resonance spectrum of the allyl (CH$_2$CHCH$_2$) radical. \vspace{1em} We have shown previously that high-resolution IR spectra of polyatomic neutral closed shell molecules can be obtained with high sensitivity by scanning the frequency of a single mode infrared optical parametric oscillator (IR-OPO) laser to excite the molecular species of interest and fixing the frequency of a tunable vacuum ultraviolet (VUV) laser to photoionize the IR excited species. The fact that this IR-VUV method is based on a VUV photoionization probe together with time of flight (TOF) mass spectrometry (MS) detection allows the identification of the neutral IR absorber, making the method applicable for IR spectroscopy measurements of radicals, isotopomers, and clusters, which normally exist as impure samples.Item MICROWAVE SPECTROSCOPY OF SEVEN CONFORMERS OF 1,2-PROPANEDIOL(Ohio State University, 2009) Neill, Justin L.; Muckle, Matt T.; Pate, Brooks H.; Lovas, F. J.; Plusquellic, D. F.; Remijan, A. J.Previously, two conformations of 1,2-propanediol have been identified by microwave spectroscopy by Caminati. \textbf{86} (1981) 193-201.} Here we report the assignment of five additional conformers, two from work on a Balle-Flygare type cavity FTMW spectrometer at NIST, operating between 8 and 26 GHz, and three from a deep average scan on the chirped pulse Fourier transform microwave (CP-FTMW) spectrometer at the University of Virginia, operating between 6.5 and 18.5 GHz. All seven of the assigned conformers contain an intramolecular hydrogen bond between the two hydroxyl groups. Stark effect measurements have been performed on the cavity FTMW spectrometer to determine the dipole moments of the three lowest energy conformers. Relative abundances of the conformers have also been determined from the CP-FTMW spectrum. A subsequent interstellar search toward Sgr B2(N) yielded negative results with an upper limit to the total column density that is less than those of glycolaldehyde and ethylene glycol.Item DENSITY FUNCTIONAL THEORY STUDY ON MOLECULAR STRUCTURE AND VIBRATIONAL SPECTRA OF 4-AMINO-1-METHYLBENZENE(Ohio State University, 2009) Kumru, M.; Bardakci, T.; Sari, L.We have discussed the applicability limits of HF, MP2 and DFT-B3LYP methods on 4-amino-1-methylbenzene in our previous work [1]. We have found the DFT-B3LYP method very promising for vibrational spectral analyses. In this study, we extend DFT calculations with different basis sets for more appropriateness to exprimental results. The optimized molecular structures, vibrational frequencies and coresponding vibrational assigments of 4-amino-1-methylbenzene have been obtained from the DFT-B3LYP, DFT-B3PW91 and DFT-PBEPBE methods implementing the 6-311G+** and aug-ccPVQZ basis sets. Scale factors, which bring computational frequencies in closer agreement with the experimental data, have been calculated for predominant vibrational motions of the normal modes at each level considered. All observed harmonic IR and Raman bands of 4-amino-1-methylbenzene have been assigned in the frameworks of the calculations. The comparison of calculations with FT-IR and FT-Raman spectra of 4-amino-1-methylbenzene have been carried out. We are planing to extend this work to the transition metal complexes in the form of MX2L2 [M: Transition metals e.g. Mn(II), Co(II) and Ni(II) . . . ; X : Halogens e.g Cl, Br, I, L: 4-amino-1-methylbenzene] 1. A. Altun, K. Golcuk, M. Kumru, "Structure and vibrational spectra of p-methylaniline: Hartree-Fock, MP2 and density functional theory studies", JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 637: 155-169 OCT 3 2003Item INFRARED SPECTRA OF CARBONYL SULFIDE-ACETYLENE TRIMERS: OCS-(C$_2$H$_2$)$_2$ AND TWO ISOMERS OF (OCS)$_2$-C$_2$H$_2$(Ohio State University, 2009) Afshari, Mahin; Dehghany, M.; Oliaee, J. N.; Moazzen-Ahmadi, N.; McKellar, A. R. W.Spectra of acetylene-carbonyl sulphide trimers in the region of the OCS \nub{1} fundamental ($\sim$2062 \wn) are observed using a tunable diode laser to probe a pulsed supersonic slit jet expansion. A previous microwave study of (OCS)$_2$- C$_2$H$_2$ by Peebles and Kuczkowski \textbf{111}, 10511 (1999).} gave a nonplanar triangular twisted structure, which could be thought of as a polar OCS dimer plus a C$_2$H$_2$ monomer lying above the dimer plane. In the present work, three infrared bands are analyzed. The first band clearly belongs to this previously known (OCS)$_2$-C$_2$H$_2$ complex. The second band can be assigned as an isomer of (OCS)$_2$-C$_2$H$_2$ having a similar structure, but with a nonpolar OCS dimer plus a C$_2$H$_2$ monomer above the dimer plane. The third band is assigned to OCS-(C$_2$H$_2$)$_2$. The rotational constants and dipole moment components of all three bands are consistent with barrel shape structures having C$_1$, C$_2$ and C$_s$ symmetries, respectively.Item THEORETICAL STUDIES OF TIME-RESOLVED PHOTOELECTRON SPECTRA OF IBr$^-$(Ohio State University, 2009) Horvath, Samantha; McCoy, Anne B.; Pitzer, Russell M.In the present study, we examine the time-resolved photoelectron spectra of IBr$^-$. In the photodetachment studies performed by Sanov and co-workers and Lineberger and co-workers,}, {\bf{2005}}, {\it{122}}, 174305; Leonid Sheps, Elisa M. Miller, and W. C. Lineberger (private communication).} the anionic species, prepared in its electronic ground state ($^2\Sigma_{1/2}^+$), is excited to either its {\it{\~{A}}}$^\prime$ ($^2\Pi_{3/2}$) or {\it{\~{B}}} ($^2\Sigma_{1/2}^+$) excited state, before electron photodetachment and dissociation on the {\it{\~{C}}} ($^1\Pi_1$) or higher-lying excited states of the neutral species, respectively. In this work, we use the electronic structure program {\it{Columbus}} to calculate the six lowest electronic states of IBr$^-$ and the ten lowest $\Sigma$ states of IBr at the MR-SO-CISD/aug-cc-pVDZ level of theory/basis, using relativistic core potentials for I and Br. Experimentally determined electronic states of IBr are also used.}, {\bf{2001}}, {\it{114}}(6), 2629.} Vibrational eigenstates for these electronic states are calculated in a discrete variable representation,}, {\bf{1992}}, {\it{96}}(3), 1982.} and propagation of the thermally populated {\it{\~{X}}}-state vibrational wave functions on either the {\it{\~{A}}}$^\prime$ or {\it{\~{B}}} electronic states of the anion is performed using a Lanczos scheme. We then take time-dependent overlaps between these propagated states and the vibrational eigenstates of the neutral surface. Results for IBr$^-$ show good agreement with the experimental time-resolved spectra. Extensions to IBr$^-$(CO$_2$)$_n$ ($n < 2$) will also be discussed.Item RAYLEIGH SCATTERING CROSS SECTION MEASUREMENTS WITH A THREE MIRROR RING CAVITY(Ohio State University, 2009) Kuramoto, Douglas S.; Zare, Richard N.; Kachanov, Alexander A.Most optical cavities in cavity ring-down spectroscopy consist of two mirrors. Using a more complicated cavity design, such as one with three mirrors, can lead to advantages such as reducing the effect of baseline variations due to reflections between the cavity mirror and the laser. A three mirror cavity in the ring configuration has been developed which uses the backward traveling wave to provide feedback to an external cavity diode laser. Measurements of Rayleigh scattering cross sections using this setup will be discussed.Item INFRARED SPECTRA OF M$^+$(2-AMINO-1-PHENYL ETHANOL)(H$_2$O)$_{n=0-2}$Ar (M=Na, K)(Ohio State University, 2009) Nicely, Amy L.; Lisy, James M.A balance of competing electrostatic and hydrogen bonding interactions directs the structure of hydrated gas-phase cluster ions. Because of this, a biologically relevant model of cluster structures should include the effects of surrounding water molecules and metal ions such as sodium and potassium, which are found in high concentrations in the bloodstream. The molecule 2-amino-1-phenyl ethanol (APE) serves as a model for the neurotransmitters ephedrine and adrenaline. The neutral APE molecule contains an internal hydrogen bond between the amino and hydroxyl groups. In the M$^+$(APE) complex, the cation can either interrupt the internal hydrogen bond or position itself above the phenyl group, leaving the internal hydrogen bond intact. The former is preferred based on DFT calculations (B3LYP/6-31+G*) for both K$^+$ and Na$^+$ across the entire range from 0-400K, but infrared photodissociation (IRPD) spectra indicate a preference for the latter configuration at low temperatures. The IRPD spectra of M$^+$(H$_2$O)$_{n=1-2}$ and M$^+$(H$_2$O)$_{n=0-2}$Ar (M=Na, K) will be presented along with parallel DFT and thermodynamics calculations to assist with the identification of the isomers present in each experiment.Item THE OPTICAL STARK SPECTRA OF CoF AND CoH(Ohio State University, 2009) Wang, Hailing; Zhuang, Xiujuan; Steimle, Timothy C.Comparing the predicted and observed permanent electric dipole moments, $\mu$$_{el}$, for simple diatomic cobalt containing molecules is a means of testing computational methodologies used for modeling cobalt-catalyzed reactions. Here we report on the experimental determination of $\mu$$_{el}$ for CoH and CoF from the analysis of the Stark shifts in the (0,0) bands of the $A^{\prime}^{3}$$\Phi_{4}-X^{3}\Phi_{4}$ system of cobalt monohydride, CoH, and the $[18.8]^{3}$$\Phi_{4}-X^{3}\Phi_{4}$ system of cobalt monofluoride, CoF. In addition, the proton magnetic hyperfine interaction in CoH is analyzed. The relative values for $\mu$$_{el}$ are rationalized using a molecular orbital correlation diagram and with high-level \textit {ab initio} predictions\underline {\textbf{126}} 144307, 2007.}.Item HOONO ISOMERIZATION TO HONO$_2$ INVOLVING CONICAL INTERSECTIONS(Ohio State University, 2009) Kumar, T. J. Dhilip; Stanton, John F.; Barker, John R.The important atmospheric reactions HO$_2$ + NO and OH + NO$_2$ lead to formation and dissociation of the cis- and trans- isomers of the HOONO complex. In the present work, the global HNO$_3$ potential energy surface (PES) is being studied by using high-level ab initio electronic structure methods. This PES, 3999 (2003).} and others in the same class have been studied previously by others. In the F + NO$_2$ reaction system, UCCSD(T) calculations showed that FONO isomerizes to FNO$_2$ through a tight transition state involving a two-state avoided curve crossing, 7639 (2004).}. A similar mechanism has been invoked for HOONO, which is isoelectronic with FONO. CASSCF multi-configurational calculations on the CH$_3$O + NO$_2$ reaction located a conical intersection near where single-configurational DFT methods predict an intrinsic energy barrier; the barrier was suggested to be an artifact$ez and J. Soto, J. Phys. Chem. A {\bf 112}, 249 (2008).}. In present work, the global HNO$_3$ PES is being investigated by both the UCCSD(T) and CASSCF methods in order to study the influence of low-lying excited electronic states on the ground state PES and reaction dynamics.Item MULTI-STATE VIBRONIC INTERACTIONS IN FLUORINATED BENZENE RADICAL CATIONS.(Ohio State University, 2009) Faraji, S.; Koppel, H.\maketitle Conical intersections of potential energy surfaces have emerged as paradigms for signalling strong nonadiabatic coupling effects . An important class of systems where some of these effects have been analyzed in the literature, are the benzene and benzenoid cations, where the electronic structure, spectroscopy, and dynamics have received great attention in the literature. In the present work a brief overview is given over our theoretical treatments of multi-mode and multi-state vibronic interactions in the benzene radical cation and some of its fluorinated derivatives. The fluorobenzene derivatives are of systematic interest for at least two different reasons. (1) The reduction of symmetry by incomplete fluorination leads to a disappearance of the Jahn-Teller effect present in the parent cation. (2) A specific, more {\em chemical} effect of fluorination consists in the energetic increase of the lowest $ \sigma$-type electronic states of the radical cations. \par The multi-mode multi-state vibronic interactions between the five lowest electronic states of the fluorobenzene radical cations are investigated theoretically, based on {\em ab initio} electronic structure data, and employing the well-established linear vibronic coupling model, augmented by quadratic coupling terms for the totally symmetric vibrational modes. Low-energy conical intersections, and strong vibronic couplings are found to prevail within the set of $\tilde{X}$--$\tilde{A}$ and $\tilde{B}$--$\tilde{C}$--$\tilde{D}$ cationic states, while the interactions between these two sets of states are found to be weaker and depend on the particular isomer. This is attributed to the different location of the minima of the various conical intersections occurring in these systems. \par Wave-packet dynamical simulations for these coupled potential energy surfaces, utilizing the powerful multi-configuration time-dependent Hartree method ckle and G.~ A.~ Worth and H.~-D.~ Meyer, {Phys.\ Rep.} {\bf 324}, 1 (2000).} are performed. Ultrafast internal conversion processes and the analysis of the MATI and photo-electron spectra shed new light on the spectroscopy and fluorescence dynamics of these species, 074310 (2008).}.Item DETECTION OF IODINE MONOXIDE RADICALS IN THE MARINE BOUNDARY LAYER USING AN OPEN-PATH CAVITY RING-DOWN SPECTROMETER(Ohio State University, 2009) Wada, Ryuichi; Beames, Joseph M.; Orr-Ewing, Andrew J.An open-path cavity ring down spectroscopy (CRDS) instrument for measurement of atmospheric iodine monoxide (IO) radicals has been tested in the laboratory and subsequently deployed in Roscoff as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project in September 2006. In situ measurements are reported of local IO mixing ratios in the marine boundary layer. \underline{\textbf{58}}, 69, 2007.} The absorption cross section at the bandhead of the IO A$^2\Pi_{3/2}$ - X$^2\Pi_{3/2}$ (3,0) vibronic band was used to obtain the mixing ratios of atmospheric IO. The mixing ratios of IO were obtained on two days, peaked close to low tide, and were ~5 - 10 times higher than values calculated from column densities previously reported by long-path, differential optical absorption spectroscopy (DOAS) in coastal regions. The typical detection limit of the instrument was estimated to be 10 pptv of IO with the total accumulation time of 30 s. The observations of relatively high concentration, compared to the values previously reported by DOAS, are consistent with the concurrent observations using a LIF (Laser induced Fluorescence) instrument. \underline{\textbf{58}}, 19, 2007.} The observed IO mixing ratios fluctuated, in part, because the open-path configurations had disadvantages that included perturbation of ring-down measurements by air currents and light scattering caused by aerosols. However these problems were more than amply compensated for by elimination of unknown sampling losses. The contribution of aerosol particles to the obtained IO mixing ratios will be discussed at the meeting.Item HIGH-RESOLUTION SPECTROSCOPY OF {$n$p} RYDBERG STATES OF He$_2$: 1. RYDBERG-STATE-RESOLVED THRESHOLD IONIZATION SPECTRA OF METASTABLE He$_2$(Ohio State University, 2009) Liu, Jinjun; Sprecher, Daniel; Raunhardt, Matthias; Schafer, Martin; Merkt, FredericA supersonic beam of metastable He$_2^*$ a $^3\Sigma_{\rm u}^+$ molecules was generated using a pulsed discharge at the exit of a pulsed valve prior to the gas expansion into vacuum.% , \emph{J. Chem. Phys.} \textbf{128}, 164310 (2008).} Transitions to high $n$p Rydberg states were recorded using photoionization and Rydberg-state-resolved threshold ionization spectroscopy.% , \emph{Chem. Phys. Lett.} \textbf{346}, 201 (2001).} Overview scans at moderate resolution (0.3 cm$^{-1}$) were obtained with ionization fields ranging from 1.3 to 133 V/cm, lowering the ionization thresholds by 5.5 and 55 cm$^{-1}$, respectively. Using a solid-state UV laser system% , \emph{Rev. Sci. Instr.} \textbf{76}, 103103 (2005).} with a 20 MHz bandwidth, high-resolution spectra of Rydberg series with $n$ up to 150 and with resolved fine structure of the initial He$_2^*$ a $^3\Sigma_{\rm u}^+$ ($N''$) state were recorded. The assignment of the observed Rydberg states is based on multichannel quantum defect theory calculations from a recent study$^a$ of pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron and photoionization spectra of He$_2$ (see following talk). %, %\emph{J. Chem. Phys.} \textbf{128}, 164310 (2008).}. The extrapolation of the observed Rydberg series to their limits enabled the determination of the ionization energy of the a $^3\Sigma_{\rm u}^+$ state and the rotational structure of the He$_2^+$ ion with a precision of better than 20 MHz.Item LABORATORY MEASUREMENT OF THE CO CAMERON BANDS AND VISIBLE EMISSIONS FOLLOWING VUV PHOTODISSOCIATION OF CO${_2}(Ohio State University, 2009) Kalogerakis, K. S.; Romanescu, C.; Slanger, T. G.; Lee, L. C.; Ahmed, M.; Wilson, K. R.The CO($\textit{a}^{3}$\Pi-$\textit{X}^{1}$$\Sigma^{+}$) Cameron bands are one of the most important emission features in the UV dayglow of the CO${_2}$ planets, as demonstrated in the case of Mars by the measurements performed by Mariner and Mars Express missions. One of the mechanisms to produce electronically excited CO($\textit{a}$^{3}\Pi$) is photodissociation of CO${_2}$ at wavelengths shorter than 108 nm. At wavelengths below 100 nm, new CO${_2}$ photodissociation channels open leading to formation of higher energy triplet states of CO. These states cascade into the lower triplet state by emission in the visible spectral region before radiating in the Cameron system. This two step relaxation pathway was demonstrated by Lee and Judge, 104 (1973)} for the 90-93 nm photodissociation of CO${_2}$. We have further investigated this process using the 85-110 nm tunable synchrotron radiation at the Advanced Light Source facility at Lawrence Berkeley Laboratory. The experimental results confirmed that once a triplet state excitation threshold is exceeded, a fraction of the Cameron band emission is accompanied by visible emission. These results indicate that the emission corresponding to the CO($\textit{a}^{\prime}$-\textit{a}, \textit{d}-\textit{a}, \textit{e}-\textit{a}) triplet bands must be part of the visible Mars / Venus dayglow. The same is true for CO${_2}$ photoexcitation in cometary atmospheres. \vspace{1em} This work was supported by the NASA Outer Planets Research Program under grant NNX06AB82G. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.Item MEASUREMENTS OF THE CO$_2$ 15 $\mu$m BAND SYSTEM BROADENED BY AIR, N$_2$ AND CO$_2$ AT TERRESTRIAL ATMOSPHERIC TEMPERATURES(Ohio State University, 2009) Smith, M. A. H.; Devi, V. Malathy; Benner, D. Chris; Blake, T. A.; Sams, R. L.In earth remote sensing, retrievals of atmospheric temperature profiles are often based on observed radiances in infrared spectral regions where emission from atmospheric CO$_2$ predominates. To achieve improved retrieval accuracy, systematic errors in the forward model must be reduced, especially those associated with errors in the spectroscopic line calculation. We have recorded more than 110 new high-resolution infrared spectra of the 15-$\mu$m band system of CO$_2$ to accurately determine line intensities, self-, air- and N$_2$-broadened widths and pressure-induced line shifts, along with their temperature dependences. The spectra were recorded with the Bruker IFS 120 HR Fourier transform spectrometer at Pacific Northwest National Laboratory (PNNL) and temperature-controlled sample cells. Sample temperatures were between 206K and 298K. Maximum total pressures were 15 Torr for self-broadening and 613 Torr for air- and N$_2$-broadening. Analysis is done using a multispectrum fitting technique, 705-721 (1995)} to retrieve the spectroscopic parameters. Line mixing and other non-Lorentz, non-Voigt line shapes are also assessed. The resulting line parameters are compared with the HITRAN database, 139-204 (2005); L.S.~Rothman et al., J. Quant. Spectrosc. Radiat. Transfer, in press (2009)} and with other measurements.Item ROTATION AND MATRIX EFFECTS ON THE EPR SPECTRA OF METHYL RADICALS TRAPPED IN GAS SOLIDS(Ohio State University, 2009) Dmitriev, Yurij A.; Benetis, Nikolas-PloutarchA study is presented on EPR spectra of methyl radicals, CH$_3$, matrix-isolated in gas solids at liquid helium temperatures. It was shown very recently \underline {\textbf{21}}(10), 103201 March 2009.} that the peculiar features of the trapped methyl rotor are attributed to the quantum effects of inertial rotary motion and its coupling to the nuclear-spin of the radical. Here, we report an investigation of the spectrum saturation behaviour and present a qualitative consideration of the spectrum anisotropy found earlier. However the broadening is by far smaller than in the expected powder of a fully anisotropic radical with rhombic $hf$-interaction and $g$-tensor anisotropy in the solid state. It is present as an asymmetric lineshape of the basic lowest rotational level EPR quartet with cross-relaxation due to the combination of the above mentioned hf interaction with the anisotropic Zeeman one. Splitting of the relatively sharp lines is also observed due to these interactions as well as due to the superimposition of the spectra of the CH$_3$ radical in other possible sites and/ or defects of the solid Kr-matrix, as well as from the first nontrivial rotational level. This is actually the only indication of the matrix interaction with the methyl radical which seems otherwise to perform almost free $3D$ rotation in the voids of the more or less ``inert'' matrix. Of course the basic reason for this behaviour is partially due to the insufficient transfer of thermal energy from the ``lattice'' to the radical motional degrees of freedom at these low temperatures of the experiments, between 1.5 and 5 K. We give prove that the anisotropy is governed, for the most part, by the repulsion interaction between the CH$_3$ radical and a matrix particle, while a matrix shift of the methyl hyperfine coupling constant is linked to both the repulsion and the attraction interactions.Item ASTRONOMICAL AND ATMOSPHERIC SPECTROSCOPY IN THE SMM/THz: EXPERIMENTS, ANALYSIS, AND CATALOGS.(Ohio State University, 2009) De Lucia, Frank C.For many years the needs of the astronomical and atmospheric science communities have directly or indirectly motivated much of the work at this symposium. Interestingly, the power and sophistication of the field instruments have grown at such a rate that the needs for laboratory data seem to be diverging rather than converging. The central role played by catalogs will be discussed, as well as their impact on the spectroscopic community.Item INVESTIGATION OF THE AMIDE I BAND OF N-METHYLACETAMIDE IN SOLID PARAHYDROGEN USING FTIR SPECTROSCOPY(Ohio State University, 2009) Paulson, Leif O.; Anderson, David T.We report the FTIR spectra of the Amide I and Amide A vibrational modes of N-methylacetamide (NMA, CH$_3$CONHCH$_3$) isolated in a solid parahydrogen (pH$_2$) matrix. NMA is one of the simplest molecules that contains the peptide bond and has therefore been the subject of numerous studies, especially those concerning peptide structure and dynamics. Solid pH$_2$ is a unique quantum solid matrix host that, among other features, allows for high-resolution IR studies of trapped dopant species. In our preliminary report, talk R008 (2006)} we showed that the Amide I lineshape was surprisingly broad and shifts were observed with small changes in temperature. That talk did not resolve the origin of these shifts with temperature that require many minutes to fully equilibrate. Further investigations have revealed that the frequency and breadth of the transition depends partially on the orthohydrogen concentration in the matrix. The Amide I lineshape displays both reversible and irreversible components that are dependent upon the temperature of the host matrix. This talk will discuss possible explanations for the breadth and temperature dependence of the Amide I feature of NMA isolated in solid pH$_2$.