title: Ultraviolet photodissociation action spectroscopy of the N-pyridinium cation.
abstract: The S1←S0 electronic transition of the N-pyridinium ion (C5H5NH(+)) is investigated using ultraviolet photodissociation (PD) spectroscopy of the bare ion and also the N2-tagged complex. Gas-phase N-pyridinium ions photodissociate by the loss of molecular hydrogen (H2) in the photon energy range 37,000-45,000 cm(-1) with structurally diagnostic ion-molecule reactions identifying the 2-pyridinylium ion as the exclusive co-product. The photodissociation action spectra reveal vibronic details that, with the aid of electronic structure calculations, support the proposal that dissociation occurs through an intramolecular rearrangement on the ground electronic state following internal conversion. Quantum chemical calculations are used to analyze the measured spectra. Most of the vibronic features are attributed to progressions of totally symmetric ring deformation modes and out-of-plane modes active in the isomerization of the planar excited state towards the non-planar excited state global minimum.
authors.affiliation: School of Chemistry, University of Wollongong, NSW 2522, Australia.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hansen
authors.affiliation: Central Analytical Research Facility, Queensland University of Technology, QLD 4000, Australia.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blanksby
authors.affiliation: School of Chemistry, The University of Melbourne, VIC 3010, Australia.
authors.forename: Nahid
authors.initials: N
authors.lastname: Chalyavi
authors.affiliation: School of Chemistry, The University of Melbourne, VIC 3010, Australia.
authors.forename: Evan J
authors.initials: EJ
authors.lastname: Bieske
authors.affiliation: School of Physics and Materials Science, University of Technology Sydney, NSW 2007, Australia.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Reimers
authors.affiliation: School of Chemistry, University of Wollongong, NSW 2522, Australia.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Trevitt