The non-symmetric ion-atom radiative processes in the stellar atmospheres

TL;DR

This paper demonstrates that non-symmetric ion-atom radiative processes significantly impact the UV and EUV opacity in stellar atmospheres, especially the solar atmosphere, and should be incorporated into models for accuracy.

Contribution

It introduces the importance of non-symmetric ion-atom processes in stellar atmosphere modeling, highlighting their comparable or greater influence than symmetric processes.

Findings

Non-symmetric processes significantly affect UV and EUV opacity.

Efficiency of these processes can surpass symmetric ion-atom absorption.

Results support including non-symmetric processes in solar atmosphere models.

Abstract

The aim of this research is to show that the processes of absorption charge-exchange and photo-association in $A+B^{+}$ collisions together with the processes of $AB^{+}$ photo-dissociation in the case of strongly non-symmetric ion-atom systems, significantly influence the opacity of stellar atmospheres in ultraviolet (UV) and extreme UV (EUV) region. In this work, the significance of such processes for solar atmosphere is studied. In the case of the solar atmosphere the absorption processes with $A=$ H and $B=$ Mg and Si are treated as dominant ones, but the cases $A=$ H and $B=$ Al and $A=$ He and $B=$ H are also taken into consideration. The choice of just these species is caused by the fact that, of the species relevant for the used solar-atmosphere model, it was only for them that we could determine the necessary characteristics of the corresponding molecular ions, i.e. the molecular potential curves and dipole matrix elements. It is shown that the efficiency of the examined non-symmetric processes within the rather wide corresponding quasi-molecular absorption bands in the far-UV and EUV regions is comparable and sometimes even greater than the intensity of the known symmetric ion-atom absorption processes, which are included now in the models of the solar atmosphere. Consequently, the presented results suggest that the non-symmetric ion-atom absorption processes also have to be included \emph{ab initio} in the corresponding models of the stellar atmospheres.