# Method for determining photoelectron angular distribution, total cross section and excitation beam polarisation from measurement of the integrated flux into selected solid angles

## Abstract

Detector geometries may be chosen to determine the total cross section sigma tot, the asymmetry parameter beta and the photo polarisation p while achieving good experimental statistics by using large acceptance angles in gas-phase photoemission experiments, in which the emitted electron current distribution is described by sigma tot(1+ beta P2(cos gamma ))/4 pi , where gamma is the angle between the emitted electron and the direction of one of the polarisation components of the photon beam. When a cylindrical mirror analyser (CMA) with variable acceptance geometry is used, it is possible to determine sigma tot, beta and the incident light polarisation p by measuring the flux with several different restricted (vignetted) annular rings whose polar and azimuthal angular acceptance ranges are appropriately chosen. The mathematical structure of this problem precludes determination of sigma tot, beta and p from the measured photocurrent using a CMA having its aperture vignetted only in the azimuthal or polar angle.