Effect of an Attractive Potential on the Classical Theory of Vibrational Energy Exchange

The usual theory of vibrational energy transfer between molecules uses a purely repulsive exponential potential with an energy zero at the bottom of the van der Waals attractive potential well. One therefore uses a velocity distribution modified by a factor exp (ε/kT) to take the attractive forces into account. This method is an artifice to avoid dealing with the detailed dynamics of motion in the attractive potential well. In the present paper, the complete dynamical problem for a ``Morse''‐type potential, consisting of an atrractive term in addition to the exponential repulsion, has been solved. A more rigorous correction for the attractive forces is therefore proposed.