Laser-induced breakdown of argon and other gases at a wavelength of 0.35 μm has been measured in the pressure range 200 to 2000 Torr. The results of short-pulse (${\tau }_p=0.4\mathrm{}$ ns) and long-pulse (${\tau }_p=500\mathrm{}$ ns) measurements in argon indicate that at $p=1\mathrm{}$ atm the breakdown threshold $I_{\mathrm{th}}$ scales as ${\tau }_p^{-0.7\mathrm{}}$. Practically complete absorption of the laser beam by the broken-down plasma has been observed at the highest pressures studied. A model for breakdown in Ar is described which gives satisfactory agreement with the data.

• Received 11 January 1982

DOI:https://doi.org/10.1103/PhysRevA.26.1164