Target excitation inH2++He collisions

The direct scattering in ${\mathrm{H}}_2^{+}$+He is studied at several energies in the range 1.0–3.0 keV. Excitation of the He target, primarily to n=2 levels, is found even at small scattering angles. The probability of exciting the He is shown to be energy dependent and in our energy and angular ranges has a maximum value of about 0.1. The experimental results are not in agreement with predictions of an extended molecular-orbital model. The same model, however, provided substantial insight into the excitation processes in the direct and electron-capture channels in ${\mathrm{He}}^{+}$+${\mathrm{H}}_2$ collisions and for collisional dissociation in ${\mathrm{H}}_2^{+}$+He→H(2p)+${\mathrm{H}}^{+}$. The excitation of the He in small-angle scattering suggests an interaction at moderate interparticle separation. Related theoretical work by Russek and Furlan [preceding paper, Phys. Rev. A 39, 5034 (1989)] addresses the excitation process.