Excitation transfer in ion—Rydberg-atom collisions

Recently, electron-loss cross sections were presented by Kim and Meyer [Phys. Rev. Lett. 44, 1047 (1980)] for 40 keV/amu ${\mathrm{N}}^{3+}$ + ${\mathrm{H}}^{**}\mathrm{}\left(n\right)\mathrm{}$ collisions which scaled as $n^{3.12}$, where $n$ is the principal quantum number of the excited ${\mathrm{H}}^0$. Such results are in contrast to an $n^2$ scaling predicted by classical and first Born theoretical methods. Our calculations indicate that a major component of the experimentally observed ion signal was due to Stark ionization by deflector grids of highly excited ${\mathrm{H}}^0$ produced in excitation-transfer collisions. Inclusion of the excitation process in a theoretical interpretation reveals qualitative agreement between theory and experiment and stresses the importance of excitation transfer in ion-Rydberg-atom collisions.