Vibrationally state-selected reactions of ammonia ions. I. NH+3(v)+D2

Resonance enhanced multiphoton ionization has been applied to the production of vibrationally state-selected ion beams. Ammonia ions are selectively formed with a specific number of vibrational quanta in the ν2 umbrella bending mode. The effect of vibrational excitation of this mode on the reaction of NH+3(X̃, v=0 to 9) with D2 is examined over the 0.5 to 10 eV center-of-mass 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 NH+3 reagent, and (3) NH2D+ is also formed by direct hydrogen–deuterium exchange of NH+3 with D2, but this channel appears as a minor contribution which is insensitive to the vibrational excitation of the NH+3. A spectator stripping model is able to account for the ratio of NH2D+ to NH3D+ as a function of the NH+3 translational and vibrational energy.