Laser Spectroscopy of a Pulsed Mercury-Helium Discharge

Following the discovery of visible laser transitions in a pulsed mercury-helium discharge, a systematic search has been made for additional laser lines between the visible region and $2\mu$. A total of 19 lines has been observed, including the four listed by Bell and two reported earlier in a continuous mercury glow discharge. Regularities in the transitions which permit laser operation indicate that population inversions among Hg ii levels arise from direct electron impact excitation from the Hg ground state, whereas inversions in Hg i more likely arise from indirect or cascade processes.