Efficient population inversion in excimer states by supersonic expansion of discharge plasmas.

Laser emission at 126 nm has been obtained from excimers of Ar(2) excited electrically in a nozzle discharge followed by supersonic expansion. The direct measurement of light amplification with a tunable VUV probe leads to a gain of >3 cm(-1). This high gain arises from efficient population inversion of low vibrational and rotational levels of the excimer state brought about by the supersonic expansion and cooling of the discharge plasma.