Enhancement of line broadening in plasmas by penetrating collisions for hydrogenlike lines

Collisions that penetrate the wavefunction extent, which are of increasing importance for more highly correlated plasmas, are not correctly accounted for by the usual long-range dipole approximation. Since the interaction is softened for penetrating collisions, a reduction in line broadening is expected and indeed this is the case with isolated ion lines. Here we report an enhancement of broadening for H-like ions due to penetration. This has a simple physical explanation and potentially important applications, for instance in line merging and dense plasmas. In addition, the so-called “strong collision” contribution, usually estimated roughly and actually dominant for highly correlated plasmas, turn out to be often negligible if penetrating collisions are correctly accounted for. It is also shown that for such plasma parameters the expected electronic temperature scaling of widths can be reversed, resulting in widths that increase with temperature.