Hydrogen spectral lines with the inclusion of dense-plasma effects

Line profiles for hydrogen including the case of dense plasmas are investigated on the basis of a many-particle approach. Using a Green's-function technique, electron contributions to the shift and broadening from both separate-level and interferencelike terms are considered consistently. The theoretical approach to the line profile has been improved by including dynamic screening of collisions, contributions from {Δ}n=0 transitions, and cross-term contributions not only to the broadening but also to the shift of the line. As an example, the line profile of H_α has been considered. An analysis of details of the second-order approximation with respect to the atom-plasma interaction is given, avoiding the no-quenching and dipole approximations. The effect of dynamic screening for high electron densities is investigated. Deviations from the linear dependence between the electron-shift contribution and the density are expected for H_α for nₑ{≥}2×{}10¹⁸ cm^-3 at temperatures of about 10 000 K.