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

TL;DR

This paper investigates non-elastic excitation and deexcitation collisions between helium Rydberg atoms and ground state helium in helium-rich white dwarf atmospheres, highlighting their significant role in atomic population dynamics.

Contribution

It demonstrates that atom-Rydberg atom processes are crucial and often dominant in influencing helium atom populations in certain white dwarf atmospheric conditions.

Findings

Atom-Rydberg processes significantly affect helium excitation in white dwarf atmospheres.

These processes are comparable or dominant over electron-atom processes in weakly ionized layers.

Implications for modeling white dwarf atmospheres and spectral analysis.

Abstract

We aim to show the importance of non-elastic excitation and deexcitation processes in $\textrm{He}^{*}(n)+ \textrm{He}(1s^{2})$ 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-$\textrm{He}^{*}(n)$ 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 $\lesssim 10^{-3}$), 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-$\textrm{He}^{*}(n)$-atom processes.