Impact-parameter dependence of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>-vacancy production in Cu-Ni collisions

Abstract

We have measured the impact-parameter ($b$) dependent probabilities ($P$) for the production of Ni (and Cu) $K$ x rays in the bombardment of thin nickel foils by 50- and 65.5-MeV Cu beams. The shape of $P(b)$ is found to be independent of nickel-foil thickness ($t$) and of the presence of a pre-exciting carbon layer, but the magnitude scale of both $P(b)$ and of the total $K$-x-ray cross section is quite dependent upon $t$ and on the presence of the carbon. The data suggest that $2p\ensuremath{\sigma}$ vacancies are being produced via $2p\ensuremath{\pi}\ensuremath{-}2p\ensuremath{\sigma}$ rotational coupling preceded by preparation of the necessary projectile $2p$ vacancies in both single- and multiple-collision processes. The shape of $P(b)$ is only qualitatively similar to that expected for the rotational-coupling process, however.