Molecular dynamics study of the collision-induced dissociation of the methyl nitrite cation

Abstract

The crossed molecular beam method was used to measure scattering dynamics of the collision-induced dissociation of the methyl nitrite cation to form NO + plus methoxy radical at center-of-mass collision energies of 3.1, 19.8, and 39.8 eV. The collisional activation mechanism is impulsive at all these energies, with most probable scattering angles of 23°, 8°, and 5°, respectively. The average conversion of translational energy into internal energy is modest, about 0.6 ± 0.5 eV and is comparable to the thermochemical threshold for this process. The distribution of kinetic energies in the product ion is quite large and increases with increasing collision energy. Rice–Ramsperger–Kassel–Marcus calculations of the rates of dissociation of the molecular ion were used to describe the dissociation of the molecular ion as a function of internal energy. Convolution of the breakdown graph, an energy distribution based upon Massey’s adiabatic criterion and kinetic energy release in the dissociation step satisfactorily rationalizes our experimental results. These results are combined with those from an earlier dynamics study of nitromethane cation to provide a general description of the role of isomerization in collision-induced dissociation occurring on their common potential energy surface.