# 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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 Title: 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 Creators: Margules, L.; Janeckova, R.; Bailleux, S.; Perrin, A.; Endres, C.; Giesen, T. F.; Schlemmer, S. Issue Date: 2008 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. URI: http://hdl.handle.net/1811/33574 Other Identifiers: 2008-RH-15