title: Communication: observation of homonuclear propensity in collisional relaxation of the 13C12CD2 (v2=1) isotopologue of acetylene by stimulated Raman spectroscopy.
abstract: We report the first experimental observation of homonuclear propensity in collisional relaxation of a polyatomic molecule. A pump-probe stimulated Raman setup is used to pump population to a single rotational level of the v(2) = 1 vibrationally excited state in (13)C(12)CD(2) and then monitor the redistribution of the rotational population that has taken place after a fixed delay. The Q-branch of the 2ν(2)-ν(2) band shows a pattern of intensity alternation between the even and the odd rotational components, with the greater intensities always corresponding to the rotational levels with the same parity as the one where all the population was initially deposited. The effect can be explained by the existence of a propensity rule that favors collisional relaxation between rovibrational levels of the same parity.
authors.affiliation: Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, 28006 Madrid, Spain. raul@iem.cfmac.csic.es
authors.forename: R Z
authors.initials: RZ
authors.lastname: Martínez
authors.forename: J L
authors.initials: JL
authors.lastname: Doménech
authors.forename: D
authors.initials: D
authors.lastname: Bermejo
authors.forename: G
authors.initials: G
authors.lastname: Di Lonardo
authors.forename: L
authors.initials: L
authors.lastname: Fusina