Vacuum ultraviolet photodissociation dynamics of N2O via the C1Π state: The N(2Dj=5/2, 3/2) + NO(X2Π) product channels.

Abstract

We study the vacuum ultraviolet photodissociation dynamics of N2O via the C1Π state by using the time-sliced velocity map ion imaging technique. Images of N(2Dj=5/2, 3/2) products from the N atom elimination channels were acquired at a set of photolysis wavelengths from 142.55 to 148.19 nm. Vibrational states of the NO(X2Π) co-fragments were partially resolved in experimental images. From these images, the product total kinetic energy release distributions (TKERs), branching ratios of the vibrational states of NO(X2Π) co-fragments, and the vibrational state specific angular anisotropy parameters (β) have been determined. Notable features were found in the experimental results: the TKERs show that the NO(X2Π) co-fragments are highly vibrationally excited. For the highly vibrationally excited state of NO(X2Π), a bimodal rotational structure is found at all the studied photolysis wavelengths. Furthermore, the vibrational state specific β values of both spin-orbit channels (j = 3/2, 5/2) clearly show a monotonic decrease as the vibrational quantum number of NO(X2Π) increases. These observations suggest that multiple dissociation pathways play a role in the formation of the N(2Dj=5/2, 3/2) + NO(X2Π) products: one corresponds to a fast dissociation pathway through the linear state (the C1Π state) following the initial excitation to a slightly bent geometry in the vicinity of the linear C1Π configuration, leading to the low rotationally excited components with relatively large β values; the other corresponds to a relatively slow dissociation pathway through the bent C(31A') or C(31A″) state, leading to moderately rotationally excited NO(X2Π) products with smaller β values.