Photodissociation dynamics of nitrous oxide: The O(1D)+N2(X1Σg+) product channel

Abstract

Photodissociation of nitrous oxide (N2O) in the ultraviolet region has been revisited by using the time-sliced velocity map ion imaging technique, due to its importance in atmospheric chemistry. The images of O(1D) photofragments are recorded at 203.814 nm and 205.472 nm in one-color experiments and at eight photolysis wavelengths between 200 and 220 nm in two-color experiments. The rotational state distributions and angular anisotropy parameters of the N2(X1Σg+) co-products are derived from the images. The results indicate that the rotational state distributions are inverted with the maximum around J≈70. The anisotropy parameter β mainly shows two declines as the N2 rotational quantum number Jincreases. According to theoretical calculations [J. Chem. Phys. 136, 044314 (2012)], the variations in β with J are caused by changes in the extent of axial recoil from a linear initial configuration. In the high-J region, however, additional torque exists on the ground state potential energy surface following nonadiabatic transitions, inducing both the additional rotational excitation and the lower β values. Compared to previous works, the two-color experiments combined with single vacuum ultraviolet photonionization of O(1D) allow us to acquire both the rotational state distribution and angular distribution accurately. This work deepens our understanding of triatomic molecule decomposition.