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7Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2018
ON THE LINEAR DISPERSION LAW OF HIGH-FREQUENCY PLASMA WAVES IN
PHOTOIONIZED PLASMA
K.Yu. Vagin1, T.V. Mamontova12, S.A. Uryupin12
1P.N.Lebedev Physical Institute of RAS, 2National Research Nuclear University MEPhI
A feature of plasmas formed during the ionization of substance atoms by laser pulse is the strong difference of arising non-equilibrium photoelectron velocity distribution from the Maxwell distribution. Due to this, the properties of photoionized plasmas, which depend on the form of the electron distribution function, differ substantially from those previously established for thermodynamically equilibrium plasmas. The explicit form of the realized non-equilibrium photoelectron velocity distribution function depends on the ionization regime of the atoms.
In this communication, we demonstrate a new common feature of quasi-potential plasma waves realized in photoionized plasmas whose electrons acquire a nonzero average velocity in the process of ionization, and the thermal spread in velocities is small. In such plasmas a linear dispersion law of high-frequency electron plasma waves is realized in a wide range of wave numbers. Under the conditions of weak collisionless damping, the frequency of such waves can be several times greater than the electron Langmuir frequency, which is not realized in the Maxwellian plasma. The described features of the plasma wave dispersion law take place, in particular, in plasmas formed as a result of the tunneling ionization of gas atoms in the field of a powerful short pulse of circularly polarized radiation, and also in plasma formed during multiphoton ionization of atoms by a laser pulse of relatively moderate intensity.
