Inverted Cusps in Electron Spectra near Zero Velocity in an Attractive Coulomb Field

Abstract

An inverted cusp in the near-zero-velocity electron-loss spectrum for a 2p (m = 0) initial state is predicted for an attractive final-state Coulomb interaction. The dip occurs in the singly differential cross section dsigma/dv/sub e/, calculated in Born approximation, at v/sub e/ = v/sub P/, where the electron velocity v/sub e/ matches the projectile velocity v/sub P/ and where the familiar cusp normally appears. The dip becomes more pronounced with increasing projectile velocities v/sub P/..-->..infinity. Its existence is traced to the odd Pi/sub z/ parity of the initial state.