Zeros in (inverse) bremsstrahlung matrix elements

C. David Shaffer^*, R. H. Pratt
Department of Physics and Astronomy, The University of Pittsburgh, Pittsburgh, Pennsylvania 15260

Sung Dahm Oh
Department of Physics, Sookmyung Women's University, Seoul, Korea

Abstract:

We discuss the possibility of zeros in the non-relativistic radiative continuum-continuum matrix element for electron-atom (inverse) bremsstrahlung. As earlier demonstrated for upward transitions from bound states, the occurrence of different signs for the free-free matrix element in limiting cases, plus the requirement of continuity, implies existence of zeros. Using knowledge of the sign of the dipole matrix element in the soft and hard photon limits with one continuum electron energy held fixed, we show that zeros can occur in the s-p matrix element. We discuss the connection of our results to elastic scattering and to Ramsauer-Townsend minima. We consider the observability of zeros in this (s-p) matrix element manifested as minima in the cross sections.