Angular correlation measurements for the electron-excited 3¹P state of helium

Abstract

Angular correlations between the scattered electrons resulting from the 11S-31P excitation process in helium and the photons emitted in the decay of the 31P state to the ground state have been measured. Data have been obtained at incident electron energies of 34.6, 45.6 and 75.6 eV for electron scattering angles up to 35 degrees . Analysis of the data gives the ratio of differential cross sections for excitation of the degenerate magnetic sublevels of the state, the magnitude of the phase difference between the corresponding excitation amplitudes and the Fano-Macek orientation and alignment parameters. Reasonable agreement is obtained between the present data at 45.6 and 75.6 eV and the original data of Eminyan et al. (1975) at 50 and 80 eV respectively. Even at these small scattering angles, no theoretical work yields values for these fundamental parameters in agreement with experiment.