Laser-induced breakdown in nitrogen and the rare gases at 0.53 and 0.357μm

Abstract

An experimental and theoretical investigation of laser-induced breakdown was carried out at 0.53 and 0.35 mu m for the following gases: N₂, Ar, Ne and Xe. A Nd:YAG laser of 15 ns pulse duration was used in its second and third harmonics. The breakdown threshold intensity I^th in the pressure range 0.2th at p=3 atm was found to be 10¹²(5*10¹¹), 8*10¹⁰(1*10¹¹), 5*10¹¹(10¹²) and 4*10¹⁰(2*10¹⁰) W cm^-2 for N₂, Ar, Ne and Xe, respectively, at 0.53 mu m (0.35 mu m). The threshold is defined as the appearance of a visible flash and/or greater than 5% absorption of beam energy. The p^-1 scaling of I^th for Ne, Ar and Xe and p^-0.6 scaling for N₂ indicates that the threshold is associated at both wavelengths with avalanche breakdown rather than multi-photon ionisation.