EFFECT OF BACK REACTION ON BROADENING OF ATOMIC SPECTRAL-LINES IN THE IMPACT APPROXIMATION

The phase shift (PS) due to a particle-perturber collision in a plasma has been investigated without using the classical straight-line path approximation. The curvilinear trajectory of the perturber is taken into account through the back reaction. The electrostatic potential interactions V approximately sigma-(l)C(l)r-l and the corresponding shifts of the energy levels DELTA-E approximately sigma-(n)C(n)r(-n) are considered by using for V the leading terms only when both, one or none of the interacting particles are charged or have a permanent electric dipole moment. Thus, the PS is parameterized by at least two indices, n and l. In general, l not-equal n. Analytic specification for eta-n,l are given for (n, l)-combinations corresponding to resonance and van der Waals type perturbations, and also to the linear and quadratic Stark effects in a perturbed system. Our approach should be especially useful at relatively high plasma densities and at the adiabatic limit.