Systematic differences in the L X-ray emission in solid and gaseous targets in small impact parameter collisions

An experimental study of the one L X-ray, one scattered particle coincidence yield in small impact parameter collisions between very heavy ions and atoms has been performed. A systematic difference between the yield in solid and gaseous targets at impact parameters below 150 fm has been observed. This difference can be related to the onset of multiple vacancy production, combined with electron capture processes which are fast enough to refill the outer shells only in solid targets.