Observation of Two-Electron Penning Ionization in a Thermal-Energy Collision

Abstract

The existence of the hybrid Penning reaction, ${\mathrm{He}}^{+}+X\ensuremath{\rightarrow}\mathrm{He}+{X}^{++}+e$, has been confirmed for thermal-energy collisions of ${\mathrm{He}}^{+}$ with Mg, Ca, Sr, Ba, Y, Ce, Yb, Sn, and Pb. A new two-electron Penning reaction, ${\mathrm{He}}^{*}+X\ensuremath{\rightarrow}\mathrm{He}+{X}^{++}+2e$, has been identified in $\mathrm{H}\mathrm{e}*$-Ce and $\mathrm{H}\mathrm{e}*$-Y collisions.