Partial Control of an Ion-Molecule Reaction by Selection of the Internal Motion of the Polyatomic Reagent Ion

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Science  14 Oct 1994:
Vol. 266, Issue 5183, pp. 259-261
DOI: 10.1126/science.266.5183.259


The ion-molecule reaction NH3+ + ND3 has been studied at various collision energies (1 to 5 electron volts in the center of mass) with preparation of the NH3+ reagent in two nearly isoenergetic vibrational states. One state corresponds to pure out-of-plane bending of the planar NH3+ ion (0.60 electron volts), whereas the other state is a combination of in-plane and out-of-plane motion (0.63 electron volts). The product branching ratios differ markedly for these two vibrational-state preparations. The differences in reactivity suggest that the in-plane totally symmetric stretching mode is essentially inactive in controlling the branching ratio of this reaction.