Kinetic description of bimolecular reactions with low energy cross sections in dilute gases

The rate ν of bimolecular chemical reaction A+A=B+C is analyzed for simple models of reactive cross sections. Collisions of particles colliding with energy E larger than a relatively low characteristic energy E _Lare either non-reactive (reversed Prigogine-Xhrouet model = rPX) or the ability to react is decreasing for E>E _L(reversed line-of-centres model = rLC). After solution of the Boltzmann equation analytical expressions for the distribution function f and the rate coefficient k have been derived. It is shown that the Arrhenius activation energy E _Ais small and even negative for sufficiently small E _L. The non-equilibrium corrections to ν are small.