Comparative data on molecular gas breakdown thresholds in high laser-radiation fields

Abstract

Breakdown threshold intensity measurements have been made in oxygen and nitrogen using single picosecond pulses from one of three laser systems operating at 1.06, 0.69 and 0.53 mu m. The results are compared with those made previously to confirm that in high radiation fields ( gamma <or=1), a breakdown threshold regime exists which is only weakly dependent on pressure, indicative of direct multiphoton ionisation.