INTERPRETATION OF SCATTERING BY CHARGED-PARTICLES AND PHOTONS

In principle, Coulomb scattering by charged particles may be described by contributions from n-photon terms, corresponding to the nth order terms in the Born expansion for charged particles. Consequently, one m ay relate scattering by charged particles to scattering by photons. Th us Raman scattering, second-order Compton scattering, the Auger effect , and two electron transitions in high velocity collisions with charge d particles are examples of processes that in principle are inter-rela ted. The probability amplitude second order in the interaction with th e incoming charged particle or photon may generally be separated into a real and an imaginary part. The real part contains an energy-conserv ing propagator and may be regarded classically, while the imaginary pa rt does not conserve energy (in accord with the Uncertainty Principle) and disappears in the limit as HBAR --> 0. These two terms are relate d by a dispersion relation. The energy non-conserving part is the same as the time ordering effect which is a measure of correlation in time . We analyze observations of the ratio of double to single ionization of helium by impact of photons and charged particles.