Photodissociation Dynamics of Nitrous Oxide near 145 nm: The O(¹S₀) and O(³P_{<i>J</i>=2,1,0}) Product Channels

We report the study of photodissociation dynamics of nitrous oxide in the vacuum ultraviolet region, using the time-sliced velocity map ion imaging technique. Ion images of the O­(¹S₀) and O­(³P_{<i>J</i>=2,1,0}) products were measured at nine photolysis wavelengths from 142.55 to 148.79 nm. The product channels O­(¹S₀) + N₂(X¹Σ_g⁺) and O­(³P_{<i>J</i>=2,1,0}) + N₂(A³Σ_u⁺) have been observed. For these dissociation channels, the total kinetic energy releases of the dissociated products were acquired. With vibrational structures of the N₂ coproducts partially resolved in the experimental images, the branching ratios of different vibrational states of the N₂ coproducts were determined, and the vibrational state specific anisotropy parameters (β values) were derived. Analysis shows that the O­(¹S₀) + N₂(X¹Σ_g⁺) channel is primarily formed via nonadiabatic couplings between the C (¹Π) state and the higher-lying D (¹Σ⁺) state of the N₂O. A moderate rotational excitation and high vibrational excitation of N₂(X¹Σ_g⁺) products have been observed through this pathway. On the other hand, for the O­(³P_{<i>J</i>=2,1,0}) + N₂(A³Σ_u⁺) channels, where a slightly higher rotational excitation of N₂ coproducts have been observed, the possible pathway would be via nonadiabatic couplings from the C (¹Π) state to the lower-lying A­(¹Σ^–)­state