The variation of the electron-photon coincidence parameters, l and x for electron excitation of 11S-21P in helium in resonance regions

Abstract
The lambda and chi coincidence parameters for the 1(sup) 1S-21P electron excitation of helium are calculated using results from an eleven-state R=matrix calculation. It is shown that in the region of resonances the parameters vary rapidly. However the rapid variation only occurs over an energy range approximately equal to the width of the resonance.