Spectroscopic investigation of laser-initiated low-pressure plasmas in atmospheric gases

Abstract

Laser-initiated breakdown of N2, O2, and Ar has been investigated at sub-atmospheric pressures using a pulsed (10-nsec) Nd:yttrium aluminum garnet (Nd:YAG) laser at 1.06 μm. Breakdown thresholds have been determined from 3 to 760 Torr, and spectral analysis of the plasma emission has been carried out at 10 and 125 Torr over the 300–600-nm range. Sharp spectral features arising from highly excited singly and multiply charged ions are reported as well as an underlying continuum at intermediate pressure. Time-resolved measurements indicate a complex kinetic dynamic optical behavior.