The intensities of the resonance lines of highly ionized hydrogen-like ions

The collisional-radiative model for the distribution of population densities among the energy states of a hydrogen-like ion plasma has been extended to lower electron densities by including the additional atomic processes of two-photon decay of the 2S level and electron- and proton-induced transitions between the component angular momentum sublevels in principal levels 2 and 3. The intensity ratio of the Lyman alpha (1S-2P) to Lyman beta (1S-3P)lines in the hydrogen-like ions (Lyman ratio) is calculated for a wide range of electron temperature and density. New experimental measurements give Lyman ratios about 60-80% of theoretical predictions, compared with about 35% for previously reported measurements. It is believed that these discrepancies are due to self-absorption.