ROTATIONAL TRANSITIONS IN THE INTERACTING $\nu_2 $, $\nu_3 $, $\nu_4$ AND $\nu_6$ BANDS OF FORMALDEHYDE IN H$_2^{12}$C$^{16}$O THE MILLIMETER RANGE FOR ASTROPHYSICAL USE
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Date
2008
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Publisher
Ohio State University
Abstract
This work, besides its fundamental interest, is motivated by the astrophysical importance of formaldehyde. For example formaldehyde was detected by millimeter techniques in Orion-KL and in several low-mass protostars }} {\textbf{526}} 845-53 (1999)}. However, no line parameters are presently available in the spectroscopic databases for the rotational transitions within the 2$^{1}$, 3$^{1}$, 4$^{1}$ and 6$^{1}$ first excited vibrational states of formaldehyde. The goal of this study is to generate a list of line parameters for these "hot" transitions in order to help such - may be - future identifications in astrophysical spectra. For this reason, submillimeter spectra were recorded at Lille and at Koln in the 150-650 and 850-900 GHz spectral ranges, respectively. These sub millimeter data were combined in a least squares fit calculation with the infrared experimental data available in the literature for the $\nu_3$, $\nu_4$ and $\nu_6$ bands }} {\textbf91}, 646 (1989)}, and for the $\nu_2$ band }} {\textbf{245}}, 141-144, (2007)}. The Hamiltonian model accounts for the various Coriolis-type resonances which perturb the energy levels of the 3$^{1}$, 4$^{1}$ and 6$^{1}$ vibrational states. In addition a weaker and somehow unexpected anharmonic resonance coupling the 2$^{1}$ and 3$^{1}$ energy levels was accounted for.Using this theoretical model, it proved possible to reproduce satisfactorily the experimental data and to generate a list of line positions and intensities for the $\nu_2~\leftrightarrow~\nu_2$, $\nu_3~\leftrightarrow~\nu_3$, $\nu_4~\leftrightarrow~\nu_4$, and $\nu_6~\leftrightarrow~\nu_6$ rotational transitions.
Description
[1]Mangum-JG ; Wootten-A ; Barsony-M , Astrophys. J.[2]D. C. Reuter, H. Takeo, S. Nadler, S.J.Daunt, and J. W. C. Johns, J. Chem. Phys.[3]F. Kwabia Tchana, A. Perrin and N. Lacome, J. Mol. Spectrosc.
Author Institution: Laboratoire PhLAM, CNRS UMR 8523, Universite de Lille 1, Bat. P5, 59655 Villeneuve d'Ascq Cedex, France.; Laboratoire Inter Universitaire des Systemes Atmospheriques, CNRS UMR 7583, Universite Paris 12, 61 Av du General de Gaulle, 94010 Creteil Cedex France.; I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany.
Author Institution: Laboratoire PhLAM, CNRS UMR 8523, Universite de Lille 1, Bat. P5, 59655 Villeneuve d'Ascq Cedex, France.; Laboratoire Inter Universitaire des Systemes Atmospheriques, CNRS UMR 7583, Universite Paris 12, 61 Av du General de Gaulle, 94010 Creteil Cedex France.; I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany.