Ion pair dissociation from N2O followed by autodetachment of N-(D-1(g))

A novel kind of ion pair dissociation, where autodetachment from the negati ve ion follows charge separation, has been observed in N2O by velocity imag ing photoionization coincidence spectroscopy. At a photon energy of 16.85 e V, electrons with a kinetic energy of similar to1.5 eV are found in coincid ence with vibrationally excited NO+(X (1)Sigma (+)). The formation mechanis m is assigned as N2O(X (1)Sigma (+)) + hv --> NO+(X (1)Sigma (+)) + N-(D-1( g)) --> NO+(X (1)Sigma (+)) + N(S-4(u)) + e(-), on the basis of the energet ics of the system and the kinetic energy distribution of the NO+ (X (1)Sigm a (+)). Asymmetry parameters fl for the electrons and NO+ ions are -0.12 +/ - 0.02 and -0.03 +/- 0.01 respectively. Lack of angular correlation between the electron and NO+ directions is interpreted as showing autodetachment a t very long range, consistent with the very long calculated lifetime of the excited N- ion. (C) 2001 Published by Elsevier Science B.V.