Intermediate-velocity atomic collisions. III. Electron capture in 8.6- MeV/amu Ca ions

Electron-capture cross sections by 8.6-MeV/amu ${\mathrm{Ca}}^{18+}$, ${\mathrm{Ca}}^{19+}$, and ${\mathrm{Ca}}^{20+}$ beams were measured in gas targets from ${\mathrm{H}}_2$ to Xe. Measurements were made of total electron capture as well as of electron capture in coincidence with projectile K x rays. Comparison with the eikonal approximation shows a reasonable agreement with the experimental data. The effect of various metastable states of the heliumlike ${\mathrm{Ca}}^{18+}$ ion created by electron capture for ${\mathrm{Ca}}^{19+}$ projectiles is analyzed, showing that these states play an important role in the detected x-ray yields.