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) ⇒ H + 2 +e, H*(n)+H(1s) ⇒ H(1s)+H + +e, and inverse recombination: H + 2 +e ⇒ H*(n)+H(1s), 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 H + 2 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 T e f f = 3800 K and find that the inclusion of chemi-ionization and chemi-recombination processes is significant in the low temperature parts of the atmosphere.