Radiative electron-capture processes in zero- and one-electron heavy-ion collisions with He

Abstract

The x rays from radiative electron capture (REC) have been observed under single-collision conditions for ${\mathrm{F}}^{8+}$ and ${\mathrm{F}}^{9+}$ ions incident on a He-gas target in the collision energy range 15 to 40 MeV. The peak energies of the REC x rays have been found to change linearly with the projectile ion energies. From extrapolation to the zero projectile energy, the binding energies of the $s$-shell electrons have been estimated to be 0.97\ifmmode\pm\else\textpm\fi{}0.02 keV for ${\mathrm{F}}^{7+}$ and 1.08\ifmmode\pm\else\textpm\fi{}0.02 keV for ${\mathrm{F}}^{8+}$ ions. These values are in agreement with theoretical predictions. It is found that the width of the REC x-ray peak for ${\mathrm{F}}^{9+}$ ions is broader than that for ${\mathrm{F}}^{8+}$ ions in contrast with a model for REC. The production cross sections of the REC x rays for ${\mathrm{F}}^{9+}$ ions are in reasonable agreement with the Bethe-Salpeter calculation. The total REC x-ray-production cross sections for ${\mathrm{F}}^{8+}$ and ${\mathrm{F}}^{9+}$ are compared with the total electron-capture cross sections.