title: Photodissociation dynamics of nitromethane and methyl nitrite by infrared multiphoton dissociation imaging with quasiclassical trajectory calculations: signatures of the roaming pathway.
abstract: We combine the techniques of infrared multiphoton dissociation (IRMPD) with state selective ion imaging to probe roaming dynamics in the unimolecular dissociation of nitromethane and methyl nitrite. Recent theoretical calculations suggest a "roaming-mediated isomerization" pathway of nitromethane to methyl nitrite prior to decomposition. State-resolved imaging of the NO product coupled with infrared multiphoton dissociation was carried out to examine this unimolecular decomposition near threshold. The IRMPD images for the NO product from nitromethane are consistent with the earlier IRMPD studies that first suggested the importance of an isomerization pathway. A significant Λ-doublet propensity is seen in nitromethane IRMPD but not methyl nitrite. The experimental observations are augmented by quasiclassical trajectory calculations for nitromethane and methyl nitrite near threshold for each dissociation pathway. The observation of distinct methoxy vibrational excitation for trajectories from nitromethane and methyl nitrite dissociation at the same total energy show that the nitromethane dissociation bears a nonstatistical signature of the roaming isomerization pathway, and this is possibly responsible for the nitromethane Λ-doublet propensity as well.
authors: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors: Arghya
authors: A
authors: Dey
authors: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors: Ravin
authors: R
authors: Fernando
authors: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors: Chamara
authors: C
authors: Abeysekera
authors: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
authors: Zahra
authors: Z
authors: Homayoon
authors: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
authors: Joel M
authors: JM
authors: Bowman
authors: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors: Arthur G
authors: AG
authors: Suits