Study of the angular distribution for the photoelectron spectra of halogen substituted methane molecules

Abstract

The intensity of photoelectrons ejected from randomly oriented gaseous molecules as a function of the angle θ between the direction of the incoming photon and outgoing photoelectron is given from theory to be 1 +β/2 ( sin²θ– 1). The angular parameter β is dependent on two factors: the photoelectron energy and the nature of the molecular orbital from which the photoelectron is ejected. Angular measurements should provide a powerful method for identifying an orbital associated with a given ionization band. The angular parameters β have been determined for most of the ionization bands found in photoelectron spectra for the following molecules: CH₃F, CH₂F₂, CHF₃, CF₄, CH₃Cl, CH₂Cl₂, CHCl₃, CCl₄, CH₃Br and CH₃I. To obtain these results, a dispersion electron spectrometer was employed, to which was attached a chamber containing a freely-rotating gas discharge lamp that provided a directed beam of HeI (584 Å) radiation. An attempt is made to correlate β with calculated population densities and atomic angular parameters. A brief discussion is also made of the dependence of β on the vibrational structure.