Impact parameter dependence ofL- andK-shell excitation in I-Ag collisions

Abstract

The impact parameter dependence of the L-and K-vacancy production of target and projectile was measured in I-Ag collisions at 40 MeV and 63 MeV in a X-ray particle coincidence experiment. A large L-vacancy production is found for impact parameters b smaller than the L-shell radius with a pronounced increase for b<250 fm. The L-shell excitation is discussed in terms of 4f~ excitation and vacancy transfer in the 3pa, 3d~z, 3 da molecular orbitals through 3 p ~-3 p a and 3 d 6-3 drc-3 d o-rotational-couplings. The 2pa excitation probability is obtained from the summed K-vacancy production probability, and compared with the prediction of 2pa excitation in a multiple collision process. The latter is determined by folding the measured I L-shell excitation probability with the impact parameter dependence of the 2p~-2pa rotational coupling. The discrepancy observed at small impact parameters suggests an enhanced 2p~ and 2pa excitation at small impact parameters in a one-collision process. The L-and K-vacancy sharing probabilities are found to be impact parameter independent over a large impact parameter range.

Systematic study of impact parameter dependent K-vacancy probabilities in near symmetric gas- and solid-target collision systems

“…The L-vacancies are then transferred to the K-shell by 2pnx-2pa rotational coupling. The measured shapes of PK(b), however, could also not be reproduced by folding the L-vacancy probability with the rotational coupling probability [24,25]. In these calculations nearly no influence of the projectile Lvacancy production in collisions prior to 2pn=-2pa rotational coupling on the shape of P,~(b) was found.…”

“…Values for these binding energies are obtained by scaling from correlation diagrams [38]. The adiabatic impact parameters calculated from this re-lation are in good agreement with the measured positions of the maxima in b. PL(b) in [34,37,25].…”

“…The systematics of the different target nuclear charge numbers Z 2 (Fig. 9) show besides a steady decrease in absolute height a steady from [25] shows, that the shape of PTc(b) does not change by more than 30 % with the choice of a stepfunction. For the determination of bLo one can certainly assume that L-vacancy production occurs in average at larger b than 2p ~x-2p cr rotational coupling.…”

“…The main contribution to the folding integral comes therefore from the region where b.PL(b ) has the maximum. On the other side one knows [25,[33][34][35][36][37] that at large b L-vacancy production in near symmetric collision systems occurs via excitation of the 4f~-molecular orbital. At our collision velocities the 4fa cannot be assumed to behave adiabatically so that direct excitation of the 4for electrons should be at large b the dominant L-vacancy production mechanism.…”