Electronic Recombination Coefficient of Molecular Helium Ions

The effect of metastable-metastable ionizing collisions has been neglected in previous measurements of the electronic recombination coefficient of molecular helium ions. In this study, a source of free electrons was taken into account and the recombination coefficient was observed to be much larger than previously reported. Over the pressure range from 15 to 50 Torr, we have measured this coefficient to range from (1.8 to 4.3) ×${10}^{-8\mathrm{}}$ ${\mathrm{cm}}^3$ ${\sec }^{-1\mathrm{}}$.