Crossed-beam measurements of differential cross sections for elastic scattering and charge exchange in low-energyHe+-He collisions

Differential cross sections for the ${\mathrm{He}}^{+}$-He collisions have been measured at eleven laboratory energies in the range 0.4-30 eV and laboratory scattering angles from 2 to 90 deg using a crossed-beam apparatus. Data are presented as absolute differential cross sections in the center-of-mass coordinate system as functions of relative translational energy and center-of-mass scattering angle. The experimental data required to establish the instrumental characteristics accurately at each energy are presented. These data will allow theoretical differential cross sections to be convoluted with the distributions characteristic of our experiments and should allow a rather precise determination of the long-range portion of the ${\mathrm{He}}^{+}$-He interaction potentials. Preliminary interpretation of the rainbow scattering data gives a dissociation energy $D_e$ for the $X{}_{}{}^2{}_{}{}^{}\Sigma _u^{+}{}_{}{}^{}$ state of ${\mathrm{He}}_2^{+}$ of 2.58±0.05 eV. This value is in good agreement with an earlier experimental result and with the most recent ab initio calculations. At relative collision energies above 1 eV, total charge-exchange cross sections obtained by integrating differential cross sections over the appropriate angular range are in reasonable agreement with previous experimental and theoretical work.