AbstractPopulations of highly‐excited states of hydrogen in gaseous nebulae are calculated including effects of lowering the atomic ionization potential. Factorsbnand dlnbn/dnwere computed for a large range of temperature and densities. Collisions only between adjacent levels (Δn= ±1) were included in the set of the statistical balance equations. Results predict the existence of a negative branch of the dlnbn/dncurve. They have to be taken into account in calculating the nebulae mod