H+D₂ reaction dynamics. Determination of the product state distributions at a collision energy of 1.3 eV

Abstract

Two-photon resonance, three-photon ionization has been used to determine the HD product internal state distribution formed by the reaction of fast H atoms with thermal D2 molecules. A mixture of HI and D2 is irradiated by a 266 nm laser pulse to dissociate the former, giving a center-of-mass collision energy of about 1.30±0.04 eV for H+D 2. After a sufficiently short delay to ensure essentially collision-free conditions, a second laser is fired which causes multiphoton ionization of individual HD quantum states as well as D atoms, depending upon the choice of wavelength. Reaction occurs in a well-defined effusive flow which emerges from a glass orifice placed between the acceleration plates of a differentially pumped time-of-flight mass spectrometer. Ion signals are referenced to those obtained from HD or D produced in an auxiliary microwave discharge. Relative formation rates are reported for HD(υ=1, J=0-6) and HD(υ=2, J=0-6). Nascent D atoms are also observed and an upper limit is placed on the production of HD(υ=3). Rotational surprisal plots are found to be linear for the HD product state distribution yielding a slope of θR=5.1 for HD(υ=1) and θR=4.7 for HD(υ=2). These are extrapolated to provide full distributions for HD(υ=0-2, J=0-6). The present product state distributions are compared with the recent experimental data of Gerrity and Valentini as well as with the quasiclassical trajectory calculations of Blais and Truhlar. © 1984 American Institute of Physics.