The Einstein equation for fluctuation probabilities of a thermodynamical system and the energy symmetrization in inelastic molecular-collision processes

Using an analogy with statistical thermodynamics and the Einstein equation for fluctuation probabilities, a fluctuation model for the inelastic collisional interaction governing molecular energy transfers is introduced. « Symmetrized» expressions respecting the detailed balance principle are obtained for the classical and semi-classical transition probabilities. These expressions are shown to be equal - within standard approximations (saddle point for perturbational integrals) - to the corre¬sponding quantum-mechanical WKB equations. Although here intro¬duced for the case of vibration-translation molecular energy transfers, the model equations reveal some generality and can be applied to a number of inelastic processes in physics. A few possible applications and developments are discussed.