Excitation and deexcitation processes in atom-Rydberg atom collisions in helium-rich white dwarf atmospheres

Abstract

We aim to show the importance of non-elastic excitation and deexcitation processes in He?(n) + He(1s2) collisions with the principal quantum number n ≥ 3 for helium-rich white dwarf atmospheres. We compare the efficiencies of these processes with those of the known non-elastic electron-He?(n) atom processes in the atmospheres of some DB white dwarfs. We show that in significant parts of the considered atmospheres, which contain weakly ionized layers (the ionization degree ≤10?3), the influence of the studied atom- Rydberg atom processes on excited helium atom populations is dominant or at least comparable to the influence of the concurrent electron-He?(n)-atom processes. © 2013 ESO.