Electron capture by slow Alq+ ions colliding with hydrogen.

Abstract

Total electron-capture cross sections have been measured for collisions of ${\mathrm{Al}}^{\mathrm{q}+}$ (q=2--10) with H and ${\mathrm{H}}_{2}$ in the 20--120-eV/amu energy range. The general trend of the cross sections for both H and ${\mathrm{H}}_{2}$ is an approximately linear increase with ionic charge state. The ${\mathrm{Al}}^{2+}$+H and ${\mathrm{Al}}^{3+}$+H systems were investigated theoretically using the molecular-orbital method with a pseudopotential to represent the ${\mathrm{Al}}^{3+}$ ion core. Coupled-channel calculations realize good agreement with experiment. An anomalously small cross section for ${\mathrm{Al}}^{2+}$+H is attributed to the fact that of the $^{1}\mathrm{\ensuremath{\Sigma}}$ and $^{3}\mathrm{\ensuremath{\Sigma}}$ entrance channels, only the $^{1}\mathrm{\ensuremath{\Sigma}}$ molecular state contributes to the cross section.