Vacuum ultraviolet fluorescence of helium in bubbles in aluminum and tin

Vacuum ultraviolet fluorescence is observed from high density helium (up to three times liquid density) in microbubbles in implanted aluminum and tin. The fluorescence is excited by bombardment with low‐energy electrons (<5 keV). The resulting spectra are attributed to a combination of excimer (higher wavelength) and atomic (lower wavelength) fluorescences. The efficiency of the process is such that it has recently been proposed for the construction of a new solid state vacuum ultraviolet photon source.