Abstract
Chemical reactions in the gas phase can often be regarded as resulting from collisions which can be idealized as motion on a potential-energy surface. An upper bound to the rate constant of such a reaction was derived by Wigner and generalized by Horiuti. Both of these workers made the additional assumption that the motion of the system on its potential-energy surface is classical. In the present paper a quantum-mechanical analog of this upper bound expression is derived for the particular case of a bimolecular reaction.