Symmetrical Chemi‐Ionization and Chemi‐Recombination Processes in Low‐Temperature Layers of Helium‐rich DB White Dwarf Atmospheres

Abstract

The influence of symmetrical chemi-ionization and chemi-recombination processes on the helium atom Rydberg states' population in weakly ionized layers of helium-rich DB white dwarfs has been investigated. The ionization processes in He à ðnÞ þ Heð1s 2 Þ collisions and their inverse recombination processes He þ 2 þ e and Heð1s 2 Þ þ He þ þ e have been considered in domains of principal quantum numbers n ! 3 and temperatures 12; 000 K T eff 30; 000 K. These processes have been treated within the frame of the semiclassical theory developed earlier. Their contributions to the Rydberg state populations have been compared with electron-electron-ion recombination, electron-excited atom ionization, and electron-ion photorecombination processes. Results showed that these processes can be dominant ionization/recombination mechanisms in helium-rich DB white dwarf atmosphere layers for log g ¼ 7 and 8 and T eff 20; 000 K and have to be implemented in relevant models of weakly ionized helium plasmas.

Influence of chemi-ionization and chemi-recombination processes on hydrogen line shapes in M dwarfs

“…Subsequently, the importance of such processes on the excited helium atom populations in atmospheres of some DB white dwarfs (Mihajlov et al 2003a) was shown.…”

The influence of -mixing processes in collisions on atoms’ populations in weakly ionized helium plasmas

“…In the case of hydrogen and helium atoms, the resonant mechanism was used to analyze the chemi-ionization and their inverse chemi-recombination processes [27][28][29][30][31][32][33]. It was shown that in weakly ionized hydrogen and helium plasmas the chemiionization/recombination processes caused by the resonant mechanism can be dominant in populating the Rydberg's states.…”

Symmetric Atom–Atom and Ion–Atom Processes in Stellar Atmospheres

“…This conclusion is based on the results obtained by Mihajlov and coworkers in [36]. The influence of symmetrical chemi-ionization and chemi-recombination processes on the helium atom Rydberg states population in weakly ionized layers of helium-rich DB white dwarfs has been investigated in [36].…”