Abstract.
Ammonia ions (NH3 +) are prepared in two internal states of nearly the same energy, a state with five quanta in the umbrella bending mode (Eint=0.60 eV) and another state with one quantum in the all-symmetric stretch and two quanta in the umbrella bending mode (Eint=0.63 eV). These ions are allowed to react with different neutral reagents, and the product ions are mass analyzed and detected. For each reaction, the product branching ratios are measured as a function of center-of-mass collision energy. Whereas reactions with D2O, D2, and CD4 are found to be uninfluenced by the state preparation of the NH3 + reagent, reactions with ND3, partially deuterated methylamine (CD3NH2), and tetrahydrofuran (c-(CH2)4O)show varying degrees of mode selectivity, the reaction with tetrahydrofuran to the least extent. We suggest that mode selectivity in these ion–molecule reactions should be a general feature when the charge transfer channel is energetically open, the geometry of the reagent ion differs markedly from the corresponding neutral, and different reaction pathways compete for product production.
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Received: 14 December 1999 / Published online: 16 August 2000
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Poutsma, J., Everest, M., Flad, J. et al. Mode selectivity in ion–molecule reactions of NH3+. Appl Phys B 71, 623–625 (2000). https://doi.org/10.1007/s003400000381
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DOI: https://doi.org/10.1007/s003400000381