Ionization and Molecular Formation in a Hydrogen-Deficient Carbon-Rich Mixture

Abstract

In this paper the ionization stage and the relationship connecting electronic pressure, gaseous pressure and temperature are studied in a H-deficient, extreme-He mixture which, also, has an overabundance of C (HdC mixture). For comparison purposes a similar analysis is made for a solar mixture and for a metal-deficient one. In our study we take account of the formation of negative ions and of molecules; the selected physical conditions roughly suit those in stellar atmospheres. The relation log (P _g /P _e) vs. log P _eis examined and their properties are interpreted. It is also shown that for those temperatures and pressures in which the main source of opacity is the Thomsons cattering, the HdC mixture is less opaque than the solar one (or the pop. II one). For low temperatures, the low abundance of C will strongly limit the formation of C^- in the HdC mixture, thus preventing it from reaching the absorbing importance of H^- in the solar one. C in the HdC mixture mimics the behavior of H in the solar one: either as an electron donor, as a maker of molecules or as a source of opacity. The similarity is qualitative only.