H-, He-like recombination spectra – V. On the dependence of the simulated line intensities on the number of electronic levels of the atoms

This paper presents a study of the dependence of the simulated intensities of recombination linesfrom hydrogen and helium atoms on the number of nl-resolved principal quantum numbersincluded in the calculations. We simulate hydrogen and helium emitting astrophysical plasmas using the code CLOUDY and show that, if not enough nl-resolved levels are included, recombination line intensities can be predicted with significant errors than can be more than 30 per cent for H I IR lines and 10 per cent for He I optical lines (∼20 per cent for He I IR recombination lines) at densities ∼ 1cm⁻³, comparable to interstellar medium. This can have consequences in several spectroscopic studies where high accuracy is required, such as primordial helium abundance determination. Our results indicate that the minimum number of resolved levels included in the simulated hydrogen and helium ions of our spectral emission models should be adjusted to the specific lines to be predicted, as well as to the temperature and density conditions of the simulated plasma.