title: Spin-torsion effects in the hyperfine structure of methanol.
abstract: The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.
authors.affiliation: Laboratoire Inter-Universitaire des Systèmes Atmosphériques, UMR 7583 CNRS-Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: L H
authors.initials: LH
authors.lastname: Coudert
authors.affiliation: Laboratoire Inter-Universitaire des Systèmes Atmosphériques, UMR 7583 CNRS-Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Gutlé
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molécules, UMR 8523 CNRS-Université Lille 1, Bâtiment P5, 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: T R
authors.initials: TR
authors.lastname: Huet
authors.affiliation: Institut für Physikalische Chemie, Callinstrasse 3-3a, 30167 Hannover, Germany.
authors.forename: J-U
authors.initials: JU
authors.lastname: Grabow
authors.affiliation: St. Petersburg Electrotechnical University "LETI," 197376 St. Petersburg, Russia.
authors.forename: S A
authors.initials: SA
authors.lastname: Levshakov