(e-2e) angular distribution studies of the cadmium 5³P ₁ autoionising state excited by 150 eV electrons

The angular correlation between scattered and ejected electrons following electron impact excitation of the 5²P₁ autoionising transition in cadmium vapour has been studied for an incident electron kinetic energy of 150 eV, using a new electron-electron coincidence spectrometer. An theoretical expression for the double diffraction cross section d² Sigma /d theta _scd theta _ej is derived by combining the autoionisation theory of Balashov et al. with the Bethe-Born scattering approximation. Good overall agreement is obtained between the theory and the experimental results.