Photoelectron Spectroscopy of the Rare Gases

A spherical retarding potential analyzer was used to measure the kinetic energies of electrons ejected by photo-ionization of the rare gases as a function of wavelength from the ²P1/2 ionization threshold down to about 400 {}. The ratio of the number of ions produced in the ground ²P3/2 state to the number produced in the excited ²P1/2 state was found to be constant with respect to wavelength and had the following values: 2.18, 1.98, 1.79, and 1.60 for Ne, Ar, Kr, and Xe, respectively. From these data the specific photo-ionization cross sections for the rare gases were obtained. At wavelengths shorter than the M₁, N₁, and O₁ thresholds for Ar, Kr, and Xe, respectively, the ejection of s electrons was observed and the specific cross sections for their production measured.