Charge Transfer to the2sState of Hydrogen from Close Collisions ofH+with He and Ar

Measurements of the electron-capture probability for close encounters in the reactions ${\mathrm{H}}^{+}+\mathrm{He}\to \mathrm{H}\mathrm{}\left(2s\right)+{\mathrm{He}}^{+}$ and ${\mathrm{H}}^{+}+\mathrm{Ar}\to \mathrm{H}\mathrm{}\left(2s\right)+{\mathrm{Ar}}^{+}$ are reported. The incident proton energies employed range from 3 to 20 keV. Measurements were made for particular impact parameters by selecting particular angles of scatter between 1 and 5 deg. The data show little angular dependence but exhibit structure as a function of collision time. For ${\mathrm{H}}^{+}+\mathrm{He}\to \mathrm{H}\mathrm{}\left(2s\right)+{\mathrm{He}}^{+}$ this structure is similar to that observed previously by Everhart and co-workers for capture into all states of hydrogen for the reaction ${\mathrm{H}}^{+}$ + He → H + ${\mathrm{He}}^{+}$, which is dominated by transfer to the $1s$ state of hydrogen. The present data are not in agreement with available coupled-state calculations for this process.