The state-to-state (vibrational-rotational) thermodn. functions developed by R. D. Levine (1976) were extended to different states. The free energy function and the chem. equilibrium constant for the atom-diatom reaction (A + BC = AB + C) were derived. Numerical calcns. were made for the reaction H + O2 = HO + O. By using the free energy and equilibrium constant values, the microscopic processes of some chem. reaction can be described as well as the effect of coupling between the vibrational and rotational states of the reactant mols. on the chem. reactivity of the system.

Key words: EQUILIBRIUM CONSTANT, THERMODYNAMIC FUNCTION, BIMOLECULAR REACTION