Non-Franck–Condon transitions in resonant autoionization of N2O

Abstract

Autoionization of N2O between 12.89 and 16.4 eV was investigated by photoionization using the pulsed synchrotron radiation from ACO, Orsay’s storage ring. Measurements were performed of threshold photoelectron spectra, photoionization spectra, and of photoelectron energy spectra. The latter were obtained from photoelectron time of flight distributions at selected wavelengths. The results suggest that autoionization in the Franck–Condon gap between the ? 2Π and the ? 2Σ+ states of N2O+ proceeds via two distinct mechanisms. The major autoionization process (?90%) produces the ? 2Π state in its low vibrational levels, while a resonant autoionization path (?10%) produces vibrationally excited ? 2Π ions. The latter process is associated with the production of low energy electrons with a distribution peaking sharply at zero energy. This resonant autoionization process appears to be a general phenomena for polyatomic molecules.