Theory of a plasma induced by resonance enhanced multi-photon ionization in inert gas

We present a model for the evolution of resonance enhanced multiphoton ionization (REMPI) produced plasma during and after the ionizing laser pulse in inert gas at arbitrary pressures. Our theory includes the complete process of the REMPI plasma generation and losses, together with the changing gas thermodynamic parameters. Plasma expansion represents a classical ambipolar diffusion. Gas heating results in a weak shock or acoustic wave. It is shown that the gas becomes involved in the motion not only by the pressure gradient due to the heating, but also because of momentum transfer from the charged particles to gas atoms. The time dependence of the total number of electrons computed in theory is in agreement with the results of coherent microwave scattering experiments.