KINETICS OF THE REACTIONS V(A4F3/2,A6D3/2) + OX (X = O, N, AND CO)

The gas-phase kinetics are reported for the reactions V(a4F3/2) + OX, Where X = 0, N, and CO, in the temperature range 297-643 K. V atoms were produced by the multiphoton dissociation of VCl4(g) at 193 nm and were detected by laser-induced fluorescence. Arrhenius rate expressions obtained for these reactions are k(02) = (1.20 +/- 0.26) x 10(-10) exp[-(2.16 +/- 0.19 kcal/mol)/RT] CM3 s-1, k(NO) = (2.20 +/- 0.26) x 10(-11) exp[-(0.40 +/- 0.19 kcal/mol)/RT] cm3 s-1, and k(CO2) = (4.38 +/- 0.62) x 10(-11) exp[-(2.90 +/- 0.14 kcal/mol)/RT]cm3 s-1, Also, room temperature rate constants were measured for the disappearance of the excited state V(a6D3/2) due to collisions with OX, Ar, and N2; the V* disappearance rates induced by collisions with the oxidants are found to be considerably faster than those of the ground-state atom, with rate constants (in units of CM3 s-1) k(02) = (1.34 +/- 0.21) x 10(-10), k(NO) = (1.00 +/-0.16) x 10(-10), k(CO2) = (2.17 +/- 0.35) X 10(-11), k(Ar) = (2.06 +/- 0.32) x 10(-13), and k(N2) = (5.62 +/- 0.83) x 10(-13). Quoted uncertainities are +/-2sigma. The rates of corrisional quenching are compared to the reaction rates of ground-state vanadium, and quenching mechanisms are discussed.