Laser Induced Avalanche Ionization in Gases or Gas Mixtures with REMPI or Femtosecond Laser Pulse Pre-Ionization

Abstract

Introduction Recently the scenario for control of ionization process in atmospheric air by dual femtosecond /nanosecond laser pulse was suggested [1]: a laser plasma may be generated by a preionizing fs pulse with a subsequent long CO2 laser pulse for additional avalanche ionization and Joule heating. A similar scenario arises in the case of the Resonance Enhanced Multiphoton Ionization (REMPI) -avalanche hybrid ionization with a nanosecond laser pulse at intensities much lower than required for breakdown of the bulk gas. That problem was studied for the Ar:Xe mixture, where during the initial portion of the pulse (3+1) REMPI of Ar atoms starts the ionization, which subsequently continues to grow with an avalanche in the buffer Xe gas [2].