Energy transfer from electronically excited atomic platinum cations to hydrogen and deuterium molecules in the gas phase at room temperature

Abstract

A novel, efficient quenching reaction for excited atomic platinum cations with hydrogen gas has been identified experimentally with an inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The rate and extent of quenching is monitored using the state-selective reaction of Pt+ with N2O and the quenching with molecular hydrogen appears to be very efficient at room temperature, the rate coefficient was measured to be approximately 3×10−10cm3molecule−1s−1. For comparative purposes, experiments also were performed with deuterium and nitrogen. The higher mass isotope deuterium appears to be slightly more efficient as a quenching agent than hydrogen, while N2 is completely ineffective as a quenching agent. An inspection of energy resonance as a criterion for collisional quenching to occur, an approach fraught with uncertainty, indicated that such a criterion is hardly useful even with the application of spectroscopic selection rules for rovibrational transitions in the diatomic quench gas. The elucidation of a quenching mechanism involving the formation and dissociation of an inserted, or partially inserted, vibrationally excited intermediate will require full computations of the relevant potential energy surfaces.