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 Title: THE MILLIMETER-WAVE SPECTRUM OF METHACROLEIN. TORSION-ROTATION-VIBRATION EFFECTS IN THE EXCITED STATES Author(s): Zakharenko, Olena Contributor(s): Huet, T.R.; Aviles Moreno, Juan-Ramon; Motiyenko, R.A. Subject(s): Atmospheric science Abstract: Last year we reported the analysis of the rotational spectrum of emph{s-trans} conformer of methacrolein CH$_{2}$=C(CH$_{3}$)CHO in the ground vibrational statefootnote{Zakharenko O. et al., 69th ISMS, 2014, TI01}. In this talk we report the study of its low lying excited vibrational states. The study is based on room-temperature absorption spectra of methacrolein recorded in the frequency range 150 � 465 GHz using the spectrometer in Lille. The new results include assignment of the first excited torsional state (131 cm$^{-1}$), and the joint analysis of the v$_{t}$ = 0 and v$_{t}$ = 1 states, that allowed us to improve the model in the frame of Rho-Axis-Method (RAM) Hamiltonian and to remove some strong correlations between parameters. Also we assigned the first excited vibrational state of the skeletal torsion mode (170 cm$^{-1}$). The inverse sequence of A and E tunneling substates as well as anomalous A-E splittings observed for the rotational lines of v$_{sk}$ = 1 state clearly indicate a coupling between methyl torsion and skeletal torsion. However we were able to fit within experimental accuracy the rotational lines of v$_{sk}$ = 1 state using the RAM Hamiltonian. Because of the inversion of the A and E tunneling substates the rotational lines of the v$_{sk}$ = 1 states were assumed to belong to a virtual first excited torsional state. Finally, we assigned several low-K$_{a}$ rotational transitions of the excited vibrational states above 200 cm$^{-1}$ but their analysis is complicated by different rotation-vibration interactions. In particular there is an evidence of the Fermi-type resonance between the second excited torsional state and the first excited state of the in-plane skeletal bending mode (265 cm$^{-1}$). \ em{Support from the French Laboratoire d�Excellence CaPPA (Chemical and Physical Properties of the Atmosphere) through contract ANR-10-LABX-0005 of the Programme d�Investissements d�Avenir is acknowledged. } Issue Date: 25-Jun-15 Publisher: International Symposium on Molecular Spectroscopy Citation Info: ACS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/79127 Date Available in IDEALS: 2016-01-05
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