A Bethe theory for the polarization of impact radiation

Abstract

On the basis of a kinematic analysis of the direction of momentum transfer, the Bethe theory is applied to the polarization of atomic line radiation by electron impact. A simple, analytic formula is obtained for the line polarization P as a function of impact energy. Comparison is made with the first Born approximation and with experiment for a number of He lines. Good agreement is generally obtained with the Born over a wide energy range, the two converging as the energy increases. Cascade effects appear insufficient to account for the gap between both theories and experiment. By using Moller's adaptation of the Bethe theory, the polarization formula is extended to relativistic impact velocities.