Laser action in the visible and ultraviolet (at wavelengths as short as 298 nm) in the higher ionization stages of a number of metal vapors has been produced by a population inversion mechanism based on segmented plasma excitation and recombination. Many of the transitions have never been observed in laser action before by any excitation means and a number of the oscillating transitions in silver, cadmium, and indium form isoelectronic sequences.
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Silfvast et al. (1981) studied this question.