A polarisation-correlation analysis of the 3¹D state of helium excited by electron impact

Abstract

In an electron-polarised-photon coincidence experiment the authors have measured the linear and circular polarisation of the 31D to 21P decay radiation (667.8 nm) emitted upon electron impact excitation of the 31D state of helium. Only photons emitted perpendicular to the scattering plane have been detected. From the experimental data target parameters are extracted which characterise the excited 31D state. The authors performed this experiment for incident-electron energies of 60, 45, 40 and 36 eV and scattering angles between 31.2 and 50'. The results are compared with a recent first-order many-body theory (FOMBT) calculation.