Calculations of Level Populations for the Low Levels of Hydrogenic Ions in Gaseous Nebulae

The level populations, b nl of hydrogen and singly ionized helium are calculated making full allowance for collisional redistribution of angular momentum and energy. In many cases the l -states are not populated statistically. Intensities of the most important line series are presented for n\, \, 40 and for a wide range of electron temperatures and electron densities. Calculated relative intensities in the spectra of H I are compared with observed intensities in the planetary nebula NGC 7662. The agreement with the photoelectric observations is good, but there is poor agreement with the photographic observations.