The production of K shell vacancies in symmetric ion-atom collisions

The electron-promotion model of Fano and Lichten (1965) has been applied to the calculation of the cross section for production of K shell vacancies in symmetric ion-atom collisions. The promotion is assumed to occur via rotational coupling between the 2p sigma and 2p pi molecular orbitals. Certain statistical factors which govern the probability of a vacancy occurring initially in the 2p pi molecular orbital have been derived. A peak in the vacancy production probability at small impact parameters is predicted and is shown to correspond to deflection through 90 degrees . Good agreement with experiment is obtained when the method is applied to the Ne + -Ne system and an approximate scaling law is suggested by which the cross section for K shell vacancy production in other symmetric collisions may be deduced.