Final-state symmetry for the n = 2 states in photoionized helium determined by theory and experiment

Experiment and theory have been used to determine the final-state symmetry for the n = 2 state in photoionized helium. The angular asymmetry parameter β has been measured as a function of photon energy by using angle-resolved photoelectron spectroscopy. From these measured β values, which are a weighted average of β/sub 2s/ and β/sub 2p/, together with the theoretical values of β/sub 2p/ and β/sub 2s/, the ratio, R, of the partial 2p photoionization cross section to the partial 2s photoionization cross section has been obtained