Measurement of absolute charge-exchange cross sections for He2+collisions with He and H2

Abstract

Reported are total, absolute charge-exchange cross sections for collisions of ${}^{3}$He${}^{2+}$ ions with He and H${}_{2}$. Measurements are reported at fixed energies between 0.33 and 4.67 keV/amu. Both the present results and earlier results of others are analyzed in terms of available experimental small-angle differential cross sections as a function of collision energy, and hence the geometry of the exit aperture of the gas-collision cells used by the various experimental groups. In addition, the effective length of gas-collision cells is studied using fluid dynamic and molecular flow simulations to address the density patterns near the cell entrance and exit apertures. When small acceptance-angle corrections were applied, the results of present and previous measurements for the single electron capture in these systems were brought into good accord in the relevant energy ranges. Taken in their entirety, the present data for ${}^{3}$He${}^{2+}$ with He and H${}_{2}$ lend themselves to new theoretical calculations of the multichannel charge-exchange cross sections.