The role of excited atomic states of a gas in the nonlinearity of the photoionized plasmas

We discuss the role of excited states of a neutral gas which is photoionize d in the regime of the barrier suppression ionization when the photoelectro ns; of the created plasmas remain in its memory on the intra-atomic electro n distribution. We obtain the strong enhancement of the inverse Bremsstrahl ung absorption of the pump field radiation and the extremely strong enhance ment of the third harmonic radiation with the increase of the principal qua ntum number of excited states of atomic electrons. (C) 2001 Elsevier Scienc e B.V. All rights reserved.