EXPERIMENTAL-EVIDENCE OF VIBRATIONAL-MODE SELECTIVITY IN THE INDIRECT PREDISSOCIATION OF N2O+ A2-SIGMA+ - ENERGY-DISTRIBUTION OF THE DIATOMIC FRAGMENT AND COMPARISON WITH A MODEL PREDICTION

The predissociation of the A 2SIGMA+ state of N2O+ has been reinvestigated with a threshold photoelectron-photoion coincidence experiment using synchrotron radiation as the excitation source and a newly designed spectrometer. The NO+ fragment vibrational distribution resulting from the predissociation of (1,0,0), (0,0,1) (2,0,0), (1,0,1), and (3,0,0) levels varies with vibrational excitation of the parent ion and in all cases is inverted and narrow. Both NO+ (X 1-SIGMA+) +N(4S0) and NO+ (X 1-SIGMA+) + N(2D0) limits are observed. Predissociation of the A state to the 2(4)SIGMA- dissociative continuum is shown to proceed via an indirect mechanism involving the 1 4-pi bound state. Close coupled quantum calculations were carried out with a simplified model for indirect predissociation in which the bending motion is neglected. They show the occurrence of vibrational population inversions in the fragment distributions, as observed experimentally.