Communication: Ultraviolet photodissociation dynamics of the simplest Criegee intermediate CH2OO

Abstract

The velocity and angular distributions of O (1)D photofragments arising from UV excitation of the CH2OO intermediate on the B (1)A' ← X (1)A' transition are characterized using velocity map ion imaging. The anisotropic angular distribution yields the orientation of the transition dipole moment, which reflects the π∗ ← π character of the electronic transition associated with the COO group. The total kinetic energy release distributions obtained at several photolysis wavelengths provide detail on the internal energy distribution of the formaldehyde cofragments and the dissociation energy of CH2OO X (1)A' to O (1)D + H2CO X (1)A1. A common termination of the total kinetic energy distributions, after accounting for the different excitation energies, gives an upper limit for the CH2OO X (1)A' dissociation energy of D0 ≤ 54 kcal mol(-1), which is compared with theoretical predictions including high level multi-reference ab initio calculations.