DYNAMIC SCREENING EFFECTS ON SEMICLASSICAL IONIZATION PROBABILITIES FOR ELECTRON-ION COLLISIONS IN WEAKLY COUPLED PLASMAS

In dense weakly coupled plasmas, dynamic screening effects on semiclas sical ionization probabilities for electron-impact ionization of hydro genic ions are investigated. The projectile target interaction Hamilto nian is obtained by introduction of the longitudinal plasma dielectric function. The semiclassical approximation is applied to treat the pro jectile electron as a classical point particle with a well-defined str aight-line trajectory R(t) and the bound electron is treated quantum m echanically. The semiclassical ionization probability is obtained as a function of the impact parameter, the projectile energy, and the Deby e length. The semiclassical ionization probability including the dynam ic screening effect is always greater than that, including the static screening effect described by the nonspherical Debye-Huckel model. Whe n the projectile velocity is smaller than the electron thermal velocit y, the dynamic screening effect turns out to be the static screening e ffect. However, when the projectile velocity is greater than the elect ron thermal velocity, the interaction Hamiltonian is almost unshielded . Unlike the electron capture processes, the difference between the dy namic and static screening effects are more significant for high-energ y projectiles. The static interaction Hamiltonian always overestimates the plasma screening effect on the electron-impact ionization process es in dense weakly coupled plasmas, (C) 1998 American Institute of Phy sics.