Isotopic replacement in ionic systems: the 4He2+ + 3He-->3He 4He+ + 4He reaction.

Full quantum dynamics calculations have been carried out for the ionic reaction (4)He(2) (+)+(3)He and state-to-state reactive probabilities have been obtained using both time-dependent and time-independent approaches. An accurate ab initio potential-energy surface has been employed for the present quantum dynamics and the two sets of results are shown to be in agreement with each other. The results for zero total angular momentum suggest a marked presence of atom exchange (isotopic replacement) reaction with probabilities as high as 60%. The reaction probabilities are only weakly dependent on the initial vibrational state of the reactants, while they are slightly more sensitive to the degree of rotational excitation. A brief discussion of the results for selected higher total angular momentum values is also presented, while the l-shifting approximation [S. K. Gray et al., Phys. Chem. Chem. Phys. 1, 1141 (1999)] has been used to provide estimates of the total reaction rates for the title process. Such rates are found to be large enough to possibly become experimentally accessible.