Dynamic screening effects on semiclassical ionization probabilities for electron-ion collisions in weakly coupled plasmas

In dense weakly coupled plasmas, dynamic screening effects on semiclassical ionization probabilities for electron-impact ionization of hydrogenic ions are investigated. The projectile target interaction Hamiltonian is obtained by introduction of the longitudinal plasma dielectric function. The semiclassical approximation is applied to treat the projectile electron as a classical point particle with a well-defined straight-line trajectory R(t) and the bound electron is treated quantum mechanically. The semiclassical ionization probability is obtained as a function of the impact parameter, the projectile energy, and the Debye length. The semiclassical ionization probability including the dynamic screening effect is always greater than that, including the static screening effect described by the nonspherical Debye-Huckel model. When the projectile velocity is smaller than the electron thermal velocity, the dynamic screening effect turns out to be the static screening effect. However, when the projectile velocity is greater than the electron thermal velocity, the interaction Hamiltonian is almost unshielded. Unlike the electron capture processes, the difference between the dynamic and static screening effects are more significant for high-energy projectiles. The static interaction Hamiltonian always overestimates the plasma screening effect on the electron-impact ionization processes in dense weakly coupled plasmas, (C) 1998 American Institute of Physics.