Interaction Energy and Mobility ofLi+Ions in Helium

The interaction energy of ${\mathrm{Li}}^{+}$ and He has been calculated for a range of internuclear separations. The results are not in very good agreement with a similar calculation by Meyerott, who used the same wave functions but approximated many of the molecular integrals. Considerable uncertainty is caused by lack of knowledge of the second-order exchange energy. The results are used to calculate the mobility of ${\mathrm{Li}}^{+}$ ions in He gas as a function of temperature for comparison with experiment. It is concluded that the theoretical interaction energy is not inconsistent with the experimental mobility data, within the uncertainty caused by the second-order exchange energy.