Statistical theory of exothermic ion-molecule reactions

A statistical theory is presented for ion-molecule reactions of the type A₂+A⁺₂A⁺₃+A, with allowance for conservation of the total energy and of the angular momentum of the composite system A⁺₄. The conservation of the momentum greatly reduces the phase volume of the initial reaction channel; the probability of decomposition in the forward direction is less than one even for exothermic reactions. A reaction of this type is considered for hydrogen, for which the statistical theory gives a qualitative explanation of the observed relation of reaction cross-section to vibrational quantum number for H⁺₂.