title: A roaming wavepacket in the dynamics of electronically excited 2-hydroxypyridine.
abstract: How much time does it take for a wavepacket to roam on a multidimensional potential energy surface? This combined theoretical and pump-probe femtosecond time experiment on 2-hydroxypyridine proposes an answer. Bypassing the well-established transition state and conical intersection relaxation pathways, this molecular system undergoes relaxation into the S1 excited state: the central ring is destabilized by the electronic excitation, within ~100 fs after absorption of the pump photon, then the H-atom bound to oxygen undergoes a roaming behavior when it couples to other degrees of freedom of the molecule. The timescale of the latter process is measured to be ~1.3 ps. Further evolution of the wavepacket is either an oscillation onto the S1 potential or a conversion into the triplet state for timescale larger than ~110 ps. Our work introduces a new tool for the understanding of time-resolved relaxation dynamics applied to large molecules through the roaming dynamics characterized by its strongly delocalized wavepacket on flat molecular potential energy surfaces.
authors.affiliation: Laboratoire Francis Perrin, CNRS-URA 2453, CEA, IRAMIS, Service des Photons Atomes et Molécules, F-91191 Gif-sur-Yvette Cedex, France. lionel.poisson@cea.fr.
authors.forename: Lionel
authors.initials: L
authors.lastname: Poisson
authors.forename: Dhananjay
authors.initials: D
authors.lastname: Nandi
authors.forename: Benoît
authors.initials: B
authors.lastname: Soep
authors.forename: Majdi
authors.initials: M
authors.lastname: Hochlaf
authors.forename: Martial
authors.initials: M
authors.lastname: Boggio-Pasqua
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Mestdagh