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 N/sup 3 +/+H**(n) collisions which scaled as n/sup 3.12/, where n is the principal quantum number of the excited H/sup 0/. Such results are in contrast to an n/sup 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 H/sup 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.