Plasma effect on tunnelling, charge transfer and transient quasimolecular states

Abstract

The influence of a dense plasma environment on electron tunnelling betweentwo ion potential wells in collectivized states and in charge-transfer collisions isstudied. We show that the tunnelling probabilities in dilute plasma (in a closeion–ion collision) and in dense plasma differ strongly. The difference is due tothe mixing between Stark components of donor-ion energy levels, caused by thefield of spectator ions in a dense plasma. The mixing is determined by an angleα between the nearest-neighbour ion field and the total electric field acting on thedonor ion. In close ion–ion binary collisions the mixing may be considered weak.However, for most plasma ions charge transfer, electron state collectivization andtransient quasimolecule formation are strongly affected by the field of spectator ions.We derive approximate analytical expressions for the distribution function ofα in an ideal plasma and perform molecular dynamics simulations to find the distribution function ofα in both ideal and nonideal plasmas. Bothα-dependentand average mixing coefficients are determined. We have found that the mixing isstrong, even in ideal plasmas, and increases further with an increase in plasmanonideality. It is shown that there is no resonant charge transfer in dense plasmas. Theapplicability of a transient ‘dicenter’ quasimolecule model for dense plasmas is discussed.