Comparison of Multiphoton and Collisional Ionization in High Intensity Laser-Plasma Interactions

Abstract

Recent multiphoton ionization experiments, performed at the University of Rochester, have shown that the tunneling ionization theories for complex atoms of Ammosov, et al. (M.V. Ammosov, et al., Sov. Phys. JEPT, 64 (1986) 1191) are valid in the regime where n* > 2 and the Keldysh tunneling parameter, γ, is less than 1. n* = Z (Eh/Eion)0.5 with Eh the ionization potential of hydrogen, and Eion that of the charge state of interest. γ = (Eion/2Φpond)0.5 where Φpond is the pondermotive potential of the laser. In high intensity laser-plasma and laser-solid interactions, tunneling ionization due to the laser field may become a dominant ionization channel. This talk will discuss the laser and plasma characteristics required for multiphoton ionization to become the dominant ionization process and the effects this has on high intensity, laser-plasma and laser-solid interactions.