H2(aΣg+3→bΣu+3)continuum emission excited by low-energy rare-gas ion collisions

Hydrogen molecules were excited into the ${\mathrm{H}}_2\mathrm{}\left(a\right)\mathrm{}$ state by impact of ${\mathrm{Ar}}^{+}$ ions in a beam at 0.5-48 eV relative energy. Optical emission in the ${\mathrm{H}}_2\mathrm{}(a-b)\mathrm{}$ continuum as well as in several H, Ar, and ${\mathrm{Ar}}^{+}$ lines was measured. Intense ${\mathrm{H}}_2\mathrm{}\left(a\right)\mathrm{}$ emission occurring below the thermodynamic threshold for ${\mathrm{H}}_2\mathrm{}\left(a\right)\mathrm{}$ excitation by ground state ${\mathrm{Ar}}^{+}$ indicates that transfer of electronic energy from metastable ${\mathrm{Ar}}^{+}$ is the dominant excitation process. The reaction is promising as a pumping mechanism for a new tunable uv laser.