Collisions of Electrons with Alkali, Alkaline and Complex Atoms Relevant to Solar and Stellar Atmospheres

Abstract

In solar and stellar atmospheres, atomic excitation by impact with electrons plays an important role in the formation of spectral lines. We make use of available experimental and theoretical cross-sections to calculate the excitation rates in s–p transitions of alkali and alkaline atoms through collisions with electrons. Then, we infer a general formula for calculating the excitation rates by using genetic programming numerical methods. We propose an extension of our approach to deduce collisional excitation rates for complex atoms and atoms with hyperfine structure. Furthermore, the developed method is also applied to determine collisional polarization transfer rates. Our results are not specific to a given atom and can be applied to any s–p atomic transition. The accuracy of our results is discussed.

Keywords

• collisions
• solar energy
• Sun: atmosphere
• stars: atmospheres
• atomic data
• light formation