Resonant auger processes for molecules as studied with angle resolved electron spectrometry

Abstract

Auger electron spectra of gaseous molecules arising from resonances that occur just below the core shell ionization potential have been measured using a variable photon source from synchrotron radiation. The systems studied include excitation from the 2 p subshells of silicon, sulfur and chlorine for SiCl 4, CS 2, COS, CCl 4, CHCl 3), CH 2Cl 2 and CH 3Cl. Simultaneous measurement of ejected electrons in both the direction of the polarization vector of the light source and perpendicularly to it have been used to assist in the deconvolution of the photoelectron spectrum of the valence orbitals from the Auger spectrum. It is found in most instances that following resonant absorption, the excited electron acts as a spectator in the Auger decay, although an instance of direct participation of the excited electron is given in the case of SiCl 4. A simple model based on spectator electron processes is discussed for correlating data on the kinetic energy of the Auger electrons with the resonance energy. Angular distribution parameters, β, have been obtained for the principal peak in the Auger spectrum as a function of photon energy for each of the molecules. The results indicate a rather flat response with β close to zero except for a slight rise at lower energies. Observations, including those on angular dependence, were also made on more highly resolved Auger spectra. The importance of multiplet splitting is discussed. An overview of the area of research on resonance Auger processes is given with suggestions for future research.