LASER-INDUCED PLASMA FORMATION IN XE, AR, N2, AND O2 AT THE 1ST 4 ND-YAG HARMONICS

Irradiance values have been measured for the onset of laser-induced plasma formation in Xe, Ar, N2 and O2 at pressures from 760 to 25 Torr at wavelengths of 1.064, 0.532, 0.355, and 0.266-mu-m. These values have been compared with the results of other workers who used similar experimental setups. There is agreement within a factor of 4 when irradiance values are compared and within a factor of 2 when ratios of irradiance values for different gasses are compared. Comparisons among workers who used widely different pulse lengths indicate that the onset of plasma formation is measured better by energy fluence than by irradiance.