Spectra of liquid helium and hydrogen-doped liquid helium

Proton-beam irradiation, using the 3 MV accelerator at Guelph, has been successful in allowing us to study the emission spectra from liquid helium and hydrogen-doped liquid helium despite the fact that the beam penetrates the target a scant 0.5 mm. H-2 emission lines can be observed from liquid samples following doping with small amounts of hydrogen into the helium gas before condensation. The line intensities are a sensitive unction of the sample temperature, becoming strongest as the liquid approaches 4.2 K. The H-2 lines themselves are much broader than those from He-2 because the helium lines actually originate in small bubbles of helium gas trapped in the liquid, which is above the lambda point The interesting fact is that electronic emission spectra from H-2 are observed at all from liquid helium and a calculation of the widths and shifts of the spectral lines will be presented.