CDW-EIS CALCULATIONS FOR RECOIL ION EMISSION IN PROTON HELIUM COLLISIONS

Single ionization of helium atoms in collision with high energy proton s is treated theoretically in the continuum distorted-wave eikonal ini tial-state (CDW-EIS) approximation. The total [E(R)] and transverse [E (R perpendicular to)] average He+ recoil-ion-energies are calculated a s functions of the laboratory proton scattering angle Theta less than or equal to 2 mrad. Measurements (Dorner et al. 1989, Phys. Rev. Lett. 63, 147-150) of these average energies made for helium gas in equilib rium at 30 K are reasonably well reproduced to within a factor of two, by the CDW-EIS approximation. The CDW-EIS recoil-ion energy distribut ions are convoluted over a Maxwellian-Boltzmann distribution, to allow for the 30 K thermal motion of the target helium atoms in the experim ent.