Analysis of particle atom collision processes, using polarized beams

Abstract

Theory of measurement for particle atom collision processes using polarized beams is presented. The density matrix formulism is applied to derive expressions for the Stokes parameters describing light emitted in particle photon coincidence experiments. These Stokes parameters in general depend on the spin polarization of the colliding particles and atoms. It is shown that an almost complete determination of scattering and target parameters is possible if one collides polarized electrons with light polarized one electron atoms. Starting with polarized electrons and polarized heavy alkalis (Cs etc.) and applying the formulism of Burke and Mitchell8 it is shown how to find the collision matrix. Some observable consequences of this formulism are also deduced. The theory of measurement for electron capture on atomic targets with polarized bare nuclei as projectiles is described in terms of Stokes parameters. This process with polarized protons is discussed as an Illustration of the theory. When the scattered hydrogen atom is not registered in coincidence with the Lyman-a resulting from the decay of H(2P)*, it is shown that circular polarization of the Lyman-a is directly proportional to the spin polarization of the protons. This relationship becomes the basis for an optical detector of the proton spin polarization. We derive expressions for the Stokes parameters in case of steady state excitation for electron atom collisions and also describe the threshold and pseudo-threshold behaviour. Some numerical calculations are plotted to illustrate the usefulness of the theory of measurement.