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Resonance enhanced multiphoton ionization has been applied to the production of vibration ally state-selected ion beams. Ammonia ions are selectively formed with a specific number of vibrational quanta in the V 2 umbrella bending mode. The effect of vibrational excitation of this mode on thereactionofNH 3 + (X, v = 0 to 9) withD 2 is examined over the 0.5 to 10eV center-ofmass kinetic energy range in a tandem quadrupole mass spectrometer. Under these conditions, ( 1) abstraction of a D atom to form NH3D + is the dominant reaction channel, (2) NH3D + having sufficient internal energy may decompose to yield NH2D + and this decomposition process is enhanced by vibrational excitation of the NH3+ reagent, and (3) NH2D + is also formed by direct hydrogen--deuterium exchange of NH3+ with D 2 , but this channel appears as a minor contribution which is insensitive to the vibrational excitation of the NH3+ . A spectator stripping model is able to account for the ratio ofNH 2 D+ to NH3D+ as a function of the NH3+ translational and vibrational energy.

The effects of vibrational excitation of the ammonia ν2 inversion mode on the reaction of NH+3(X̃,v=0 to 9) with methane have been measured in a tandem quadrupole mass spectrometer over the center-of-mass collision energy range 1.5 to 10 eV. The hydrogen abstraction channel is enhanced by nearly a factor of 2 at nine quanta of vibrational energy relative to the v=0 level of the ion. Added vibration in the ammonia ion umbrella-bending mode facilitates the transition to the NH+4 product ion geometry. Protonated methylamine is formed at lower kinetic energies by attack of the ion at the methane carbon center, but with increasing vibrational excitation of the ammonia ion, the protonated methylamine decomposes by 1,2-elimination of molecular hydrogen and by C–N bond scission.