Stark broadening of the hydrogen Hsub(α) line at low densities: fine structure and spontaneous emission effects

Taking the Hsub(α) line as a test case, the authors give a proper treatment of the broadening including energy splitting and spontaneous emission effects. At low perturber densities from (1010 to 1014 cm-3) the profile is calculated in the line centre within the impact approximation. Each collision is well described by a semiclassical perturbational approach. The energy separation of the sublevels for n = 2 and n = 3 produces a splitting of the line into seven components and modifies the collisional cross sections. These components, well resolved at perturber densities lower than 1012 cm-3, are gradually mixed for increasing densities. (author)