Depletion kinetics of nickel atoms by sulfur dioxide

The gas-phase depletion kinetics of Ni(a(3)F(J), a(3)D(J)) in the presence of SO2 are reported. Nickel atoms were produced by the 248 nm photodissocia tion of nickelocene and detected by laser-induced fluorescence. The ground term of Ni, a(3)F(4), and the two lowest energy spin-orbit states, a(3)D(3) and a(3)D(2), were found to react termolecularly (and with identical rate constants) with SO2, an indication of rapid interconversion between these s tates. The limiting low-pressure third-order rate constant, measured over t he temperature range 296-612 K, can be expressed as k(o)(T) = 7.455-24.41(l og T) + 3.993(log T)(2) cm(6) molecule(-1) s(-1). A binding energy of 47 kc al mol(-1) was estimated by combining the kinetic results with unimolecular rate theory and density functional methods. The limiting high-pressure sec ond-order rate constant over the temperature range is on the order of the c ollision rate. The other spin-orbit states of both terms depleted quite rap idly in the presence of SO2, with rate constants also on the order of the c ollision rate.