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 ${\text{He}}^{\ast }(n)+\text{He}(1s^2)$ collisions with the principal quantum number $n\ge 3$ for helium-rich white dwarf atmospheres. We compare the efficiencies of these processes with those of the known non-elastic electron-${\text{He}}^{\ast }(n)$ 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 $\lesssim 10^{-3}$), 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-${\text{He}}^{\ast }(n)$-atom processes.

Astronomy & Astrophysics, Accepted: 14 February 2013

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