Theory of steady-state breakdown of gases near metal surfaces

A theoretical study is made of the causes of plasma jet formation near metal surfaces subjected to radiation of power densities of the order of 1 MW/cm² (low-threshold breakdown). It is shown that the physical nature of this phenomenon may be similar to that of the ignition of chemical combustion reactions by a hot surface. Breakdown occurs due to thermal ionization of the metal vapor, even though the amount of material evaporated is very small. The influence of diffusion and excess heating of the electrons on the value of the threshold power density is analyzed.