Effective plasma potentials for atomic processes in plasmas

The plasma environmental effects on atomic reaction rates are formulated in terms of effective plasma potentials (EPP), which depend explicitly on the plasma densities and temperatures. The plasma effects include both the collisional transitions and field distortions of atomic states by plasma electrons and ions, and predominantly affect the high Rydberg states of excited atoms in plasmas. The EPP are obtained by averaging the atom-plasma interactions over the plasma density and velocity distribution, and designed to treat both the field distortion and collisional transition effects in a coherent and nonperturbative way. Different averaging procedures are adopted for plasma electrons and for plasma ions, depending on their characteristic relaxation times relative to the atomic processes. It departs significantly from the conventional pressure broadening theory, and also from the rate equations treatment. Evaluation of the plasma-potential corrected rates for the direct and resonant collision processes is discussed, and an analogy of the plasma effects to noisy laser-atom interactions is pointed out.