Dissociative photoionization of N2O in the region of the N2O+(C 2Σ+) state, studied by ion–electron velocity vector correlation

Abstract

Imaging and time-of-flight-resolved coincidence techniques are combined to extend the (VA+,Ve,P) vector correlation method to the study of dissociative photoionization of small polyatomic molecules breaking into two heavy fragments. Dissociative photoionization (DPI) of the N2O linear molecule into the N2O+(C 2Σ+) ionic state, induced by linearly polarized synchrotron radiation (P), is chosen as an example. The ion–electron kinetic energy correlation enables the identification of all the DPI processes producing the NO+, N+, N2+, and O+ fragments. The IχA+(θe,φe) molecular frame photoelectron angular distributions (MFPADs), deduced from the spatial analysis of the (VNO+/N+,Ve,P) vector correlations, exhibit remarkable features. When the N2O molecule is aligned parallel to the polarization axis, a preferred electron emission from the N2O+ molecular ion in the direction perpendicular to the molecular axis, as well as a strong forward–backward asymmetry that favors electron emission along the molecular axis in the same direction as the N+ or N fragment, are demonstrated. The measured MFPADs are found in good agreement with the reported multichannel Schwinger configuration interaction calculations, when molecular rotation prior to dissociation is taken into account. This comparison provides an estimation of the lifetime of the N2O+(C 2Σ+) state prior to dissociation into the dominant channels [NO+(X 1Σ+)+N(2P)] and [N+(3P)+NO(X 2Π)], which is found to be about 2 ps.