X-Ray Emission in Heavy Ion Collisions

Abstract

In this paper a review will be given on three topics currently being studied through X-ray emission produced by atomic collisions with highly ionized projectiles. These are: 1) Mechanisms for nonstatistical substate populations deduced from measurement of the linear polarization of K X-rays. 2) Mechanisms for K vacancy production in atomic collisions deduced from K X-ray–scattered particle coincidence measurements. 3) Multiple K vacancy production and sharing, and decay as deduced from X-ray-X–ray coincidence experiments. K X-ray polarization data will be presented to support relatively simple models of preferential substate populations predicted for ionization, excitation, and electron capture processes. The importance of spin-orbit relaxation and the effect of cascades on the observed X-ray polarization has been experimentally investigated and will be reviewed. Data showing the impact parameter dependence of inner shell vacancy production by direct ionization, 2pσ-2pπ rotational coupling, and electron capture will be presented. Disagreements with current theoretical models have been documented and will be emphasized. The large probability for inner shell vacancy production in heavy ion collisions makes the study of multiple vacancy decay by photon-photon coincidence techniques particularly attractive. Use of both real and random coincidence events provide Direct experimental measurement of multiple vacancy production, hypersatellite spectroscopy, vacancy sharing between separating atoms, and branching ratios between competing decay channels.