Gas Breakdown with 10.6-μ-Wavelength CO2 Laser Radiation

The gas-breakdown threshold or the minimum power density required to ionize a gas with 10.6-μ-wave-length radiation has been examined using the radiation of a Q-switched CO2 laser. The studies show that the focused beam cannot initiate the breakdown process for intensities as high as 109 W/cm2. If an initial low degree of ionization is provided by an external source, the subsequent growth of the breakdown is in agreement with a cascade model as evidenced by the experimentally determined gas pressure and laser-radiation frequency dependence.