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

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) double right arrow H-2(+) + e, H*(n) + H(1s) double right arrow H(1s) + H+ + e, and inverse recombination: H-2(+) + e double right arrow H*(n) + H(1s), H(1s) + H+ + e double right arrow H*(n) + H(1s), where H*(n) is the hydrogen atom in a state with the principal quantum number n much greater than 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-eff = 3800 K and find that the inclusion of chemi-ionization and chemi-recombination processes is significant in the low temperature parts of the atmosphere.