Influence of chemi-ionization and chemi-recombination processes on the population of hydrogen Rydberg states in atmospheres of late type dwarfs

Abstract

We study the influence of a group of chemi-ionization and chemi-recombination processes on the populations of higher states of hydrogen in the layers of a stellar atmosphere. The group of processes includes ionization: H*(n) + H(1s) ⇒ H2+ + e, H*(n) + H(1s) ⇒ H(1s) + H+ + e, and inverse recombination: H2+ + e ⇒ H*(n) + H(1s) + H+ + e ⇒ H*(n) + H(1s), where H*(n) is the hydrogen atom in a state with the principal quantum number n ≫ 1, and H2+ is the hydrogen molecular ion in a weakly bound rho-vibrational state of the ground state. These processes have been treated within the framework of the semi-classical approximation, developed in several previous papers, and have been included in the general stellar atmosphere code PHOENIX. We present results for an M dwarf atmosphere with Teff = 3800 K and find that the inclusion of chemi-ionization and chemi-recombination processes is significant in the low temperature parts of the atmosphere.