Angular differential cross sections for 25-, 50-, and 100-keV-proton excitation of helium to then=2level

Abstract

Differential cross sections for 25-, 50-, and 100-keV-proton excitation of helium to the $n=2\mathrm{}$ level have been determined for center-of-mass scattering angles from 0 to 1.2 mrad. The cross sections were obtained from an analysis of the angular distribution of the scattered protons which had lost an energy corresponding to the excitation of the helium target to its $n=2\mathrm{}$ level. The differential cross section is very sharply peaked in the forward direction and decreases by a factor of 45 in 1.0 mrad at 25 keV and by a factor of 650 in 1.0 mrad at 100 keV. The data are in excellent agreement with a recent multistate eikonal calculation.