title: Multiple product pathways in photodissociation of nitromethane at 213 nm.
abstract: In this paper, we present a photodissociation dynamics study of nitromethane at 213 nm in the π → π(*) transition. Resonantly enhanced multiphoton ionization spectroscopy and ion-imaging were applied to measure the internal state distributions and state-resolved scattering distributions of the CH3, NO(X (2)Π, A (2)Σ(+)), and O((3)PJ) photofragments. The rotationally state-resolved scattering distribution of the CH3 fragment showed two velocity components, of which the slower one decreased the relative intensity as the rotational and vibrational excitations. The translational energy distribution of the faster CH3 fragment indicated the production of the NO2 counter-product in the electronic excited state, wherein 1 (2)B2 was the most probable. The NO(v = 0) fragment exhibited a bimodal translational energy distribution, whereas the NO(v = 1 and 2) fragment exhibited a single translational energy component with a relatively larger internal energy. The translational energy of a portion of the O((3)PJ) photofragment was found to be higher than the one-photon dissociation threshold, indicating the two-photon process involved. The NO(A (2)Σ(+)) fragment, which was detected by ionization spectroscopy via the Rydberg ← A (2)Σ(+) transition, also required two-photon energy. These experimental data corroborate the existence of competing photodissociation product pathways, CH3 + NO2,CH3 + NO + O,CH3O + NO, and CH3NO + O, following the π → π(*) transition. The origins of the observed photofragments are discussed in this report along with recent theoretical studies and previous dynamics experiments performed at 193 nm.
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Sumida
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Kohge
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Yamasaki
authors.affiliation: Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kohguchi