title: Two-photon state selection and angular momentum polarization probed by velocity map imaging: application to H atom photofragment angular distributions from the photodissociation of two-photon state selected HCl and HBr.
abstract: A formalism for calculating the angular momentum polarization of an atom or a molecule following two-photon excitation of a J-selected state is presented. This formalism is used to interpret the H atom photofragment angular distributions from single-photon dissociation of two-photon rovibronically state selected HCl and HBr prepared via a Q-branch transition. By comparison of the angular distributions measured using the velocity map imaging technique with the theoretical model it is shown that single-photon dissociation of two-photon prepared states can be used for pathway identification, allowing for the identification of the virtual state symmetry in the two-photon absorption and/or the symmetry of the dissociative state. It is also shown that under conditions of excitation with circularly polarized light, or for excitation via non-Q-branch transitions with linearly polarized light the angular momentum polarization is independent of the dynamics of the two-photon transition and analytically computable.
authors.affiliation: Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors.forename: Sergei
authors.initials: S
authors.lastname: Manzhos
authors.forename: Constantin
authors.initials: C
authors.lastname: Romanescu
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Loock
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Underwood