Quasi-equilibrium thermodynamic models are proposed for describing thermochemical processes in flame and electrothermal atomizers. The conditions under which AlF molecules, which are applicable to molecular-absorption determination of fluorine, are formed in acetylene-nitrous oxide, acetylene-air, and hydrogen-air flames; on a graphite rod; and in a graphite furnace were studied by thermodynamic simulation. The main conditions theoretically predicted to be optimum for determining fluorine with the use of different atomizers correspond reasonably well to the experimental data. The models developed may be extended to other cases of analysis by molecular-absorption spectroscopy in various applications. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing.