Photodissociation Dynamics of Nitrous Oxide: The O(¹D) + N₂(X¹Σ_\textg^\text+) Product Channel^†

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(X¹\Sigma_\rmg^+ ) 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 J increases. 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.