Atomic collisions with relativistic heavy ions. VI. Radiative processes

Abstract

Besides characteristic target and projectile x rays, x-ray continua and radiative-electron-capture photons are seen in collisions with relativistic heavy ions ranging in energy from 82 to 422 MeV/amu and in atomic number from Xe to U. The angular distribution, centroid energy, cross section, and line shape of the broad radiative-electron-capture lines are analyzed. The observed continua are due to primary- and secondary-electron bremsstrahlung. In the projectile frame, primary bremsstrahlung is the radiative scattering of incident target electrons from the projectile nucleus. The continuum cross sections and angular distributions are calculated, and are compared with experiment. Secondary-electron bremsstrahlung, due to the radiative scattering of ionized target electrons from other target nuclei, is target-thickness dependent, and the cross section increases roughly with the square of the target atomic number. The calculated primary-electron bremsstrahlung cross sections are lower than experiment.