Scattering Cross Sections and Interaction Energies of Low-VelocityHe+Ions in Helium

Abstract

It is pointed out that the determination of ion-molecule forces from results of measurements of scattering of low-velocity ion beams in gases can be seriously in error unless some a priori knowledge of the nature of the forces is available. The scattering of ${\mathrm{He}}^{+}$ in He is chosen as an illustration. The elastic and charge exchange cross sections calculated from Moiseiwitsch's theoretical force laws are shown to be in good agreement with the experimental values of Cramer and Simons. The force law determined by the latter authors directly from their measurements is in error because of the assumption of an incorrect form and the failure to consider the two interaction states involved.