title: Torsion-rotation-vibration effects in the ground and first excited states of methacrolein, a major atmospheric oxidation product of isoprene.
abstract: Methacrolein is a major oxidation product of isoprene emitted in the troposphere. New spectroscopy information is provided with the aim to allow unambiguous identification of this complex molecule, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. For the most stable s-trans conformer of atmospheric interest, the torsional and rotational structures have been characterized for the ground state, the first excited methyl torsional state (ν27), and the first excited skeletal torsional state (ν26). The inverse sequence of A and E tunneling sub-states as well as anomalous A-E splittings observed for the rotational lines of v26 = 1 state clearly indicates a coupling between methyl torsion and skeletal torsion. A comprehensive set of molecular parameters has been obtained. The far infrared spectrum of Durig et al. [Spectrochim. Acta, Part A 42, 89-103 (1986)] was reproduced, and a Fermi interaction between ν25 and 2ν27 was evidenced.
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS - Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: O
authors.initials: O
authors.lastname: Zakharenko
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS - Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: R A
authors.initials: RA
authors.lastname: Motiyenko
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS - Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: J-R
authors.initials: JR
authors.lastname: Aviles Moreno
authors.affiliation: Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Jabri
authors.affiliation: Laboratoire Inter-universitaire des Systèmes Atmosphériques, CNRS - Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: I
authors.initials: I
authors.lastname: Kleiner
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molécules, UMR8523 CNRS - Université Lille 1, Bâtiment P5, F- 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: T R
authors.initials: TR
authors.lastname: Huet