Photoionization Mass Spectrometry of Kinetic energy-selected ions. An Ion Retarding Potential Difference method applied to NO+ and O+ from N2O.

A new method is described to obtain photoionization efficiency curves of kinetic energy-selected fragment ions. The method is tested and discussed in the case of the dissociative photoionization yields of NO+ and O+ from N2O. The attention is focussed on the dissociative autoionization processes in the threshold region, in the Franck-Condon region of the N2O(A2Sigma+) state and in the Franck-Condon gap between the A2Sigma+ and B2Pi states.