Electron cascade theory in laser-induced breakdown of preionized gases

Calculations are presented which follow the time evolution of the energy distribution function of electrons interacting with an extensively preionized He gas and a CO2 laser photon field. Explicit account is taken of electron-electron collisions, inelastic and superelastic collisions between electrons and excited species, and inverse bremsstrahlung in the field of ions and neutrals. Computed breakdown thresholds are in agreement with recent data of Brown and Smith.