Photoionization processes at threshold. I. Threshold photoelectron and photoionization spectra of CO2

摘要

A threshold photoelectron spectrometer is described. The instrument has a resolution (FWHM) of 14 meV for states reached by direct photoionization, and 90percnt; rejection of electrons from autoionizing events occuring more than 30 meV above direct ionization thresholds. Detailed threshold photoelectron and total photoionization efficiency spectra are presented for three electronic states (2Pgr;g,2Pgr;u,2Sgr;+u) of the CO+2ion. Vibrational excitation in the symmetric stretching mode is observed for each state with the longest progression occuring for the2Pgr;ustate. Spinndash;orbit splitting of the2Pgr;gstate is readily visible. Autoionization occurs in the vicinity of most of the2Pgr;gand2Pgr;ulevels. There is some indication for production of ions with vibrational excitation in the bending mode.