Effect of nuclear spin of a homonuclear molecule on the rate of ion capture Original Research Article

Calculations employing statistical adiabatic channel model show that the spin of a nucleus in a homonuclear molecule affects the rate of ion capture at low temperatures. Whereas for bosons in even electronic states with respect to permutation of the nuclear coordinates (Σ+g,Σ−u) the ion capture rate decreases as the spin increases, for fermions in such states the situation is reversed; the capture rate increases with increasing spin. For the odd Σ+u,Σ−g states the trends are reversed. Such trends are exhibited over the whole region of low temperatures. At very low temperatures the spin effects can become very large. If the effect of the reduced mass contributed by the Langevin rate constant can be ignored, the normal kinetic order at which the isotopomeric molecules capture an ion is reversed. For instance, C2T2+H+3 occurs slower than does C2D2+H+3.