Angular correlations between electrons and photons in the electron excitation of helium and neon

Abstract

Angular correlations have been measured between the electrons exciting the 2¹P state in helium and the photons arising from the decay of this state to the ground state. Analysis of these angular correlations yields the ratio lambda of the differential cross sections for the excitation of the m=1 and m=0 magnetic substates, and the relative phase chi of the scattering amplitudes for the excitation of these substates. The parameters lambda and chi have been measured at 80 eV and 120 eV and scattering angles between 10 degrees and 16 degrees . The data are compared with the predictions of the first Born approximation and the Glauber approximation which show relatively good agreement for lambda but poor agreement for the relative phase chi . Data are presented for the parameters lambda and chi for the excitation of the resonant 3¹P₁ state in neon.