ANOMALOUS FINAL-STATE DISTRIBUTIONS OF ELECTRONS CAPTURED FROM DIRECTED RYDBERG STATES

A classical model of singly charged ion collisions with Rydberg atoms in linear Stark states directed toward the oncoming ion beam predicts a bimodal distribution of final states resulting from electron capture . At a reduced velocity <(upsilon)over tilde> = upsilon(ion)/upsilon(B ohr) = 0.45, the calculated energy distribution of captured electrons peaks near the target binding energy E-i, but has a second peak at ene rgies roughly E-i/4. Analysis of the impact-parameter dependence of th e capture probabilities indicates that the second peak arises from thr ee-swap capture events. The decrease in binding energy of the captured electrons is attributed to excitation via united-atom rotational coup ling. [S1050-2947(98)50401-5].