Optical breakdown in metal vapours

Abstract

Mercury, caesium and rubidium vapours have been ionized in the intense radiation flux produced by a Q-switched ruby laser. The technique used is applicable to metals which can be handled in vapour tubes. The characteristic threshold for breakdown of the vapours appears at a density of 1·3 × 1020 atoms/cm3 for mercury, 1·2 × 1016 atoms/cm3 for caesium and 5 × 1016 atoms/cm3 for rubidium, for a radiation flux of 5 × 109 w cm-2. These results are compared with measurements by Meyerand and Haught in 1963 which give thresholds at densities of 4·8 × 1020 atoms/cm3 for argon and 3·4 × 1021 atoms/cm3 for helium at the same flux.