TEMPERATURE-DEPENDENT STUDY OF THE GAS-PHASE KINETICS OF ZR(A(3)F(2))AND HF(A(3)F(2))

The second-order rate constants of gas-phase Zr(a F-3(2)) and Hf(a F-3 (2)) With O-2, N2O, CO2, NO, H2O, SO2 and SF6 as a function of tempera ture are reported. For Zr(a F-3(2)), th, bimolecular rate constants ti n molecule(-1) cm(3) s(-1)) are described in Arrhenius form by k(O-2) = (2.6 +/- 0.5) x 10(-10) exp(- 6.2 +/- 0.7 kJ mol(-1)/RT), k(N2O) = ( 1.6 +/- 0.3) x 10(-10) exp(-3.3 +/- 0.6 kJ mol(-1)/RT), k(CO2) = (1.4 +/- 0.2) x 10(-10) exp(-5.1 +/- 0.4 kJ mol(-1)/RT), k(NO)=(1.6 +/- 0.3 ) x 10(-10) exp(-1.9 +/- 0.5 kJ mol(-1)/RT) and k(SF6)= (3.4 +/- 1.3) x 10(-10) exp(-28 +/- 2 kJ mol(-1)/RT), where the uncertainties are +/ -2 sigma. The rate constants for Zr reacting with H2O and SO2 were tem perature insensitive with room-temperature rate constants of 9.1 x 10( -11) and 3.5 x 10(-10) molecule(-1) cm(3) s(-1), respectively. For Hf( a F-3(2)), the bimolecular rate constants are described in Arrhenius f orm by k(O-2) = (1.2 +/- 0.1) x 10(-10) exp(-2.8 +/- 0.3 kJ mol(-1)/RT ), k(N2O) = (1.5 +/- 0.2) x 10(-10) exp(-11.3 +/- 0.5 kJ mol(-1)/RT), k(CO2)=(1.4 +/- 0.2) x 10(-10) exp(-17.5 +/- 1.2 kJ mol(-1)/RT), k(H2O )= (2.1 +/- 0.3) x 10(-11) exp(-3.4 +/- 0.6 kJ mol(-1)/RT), k(SF6)= (7 +/- 5) x 10(-10) exp(-41 +/- 3 kJ mol(-1)/RT). The rate constants for Hf reacting with NO and SO2 were temperature insensitive with room-te mperature rate constants of 1.0 x 10(-10) and 3.0 x 10-10 molecule(-1) cm(3) s(-1), respectively. The disappearance rates for all the reacta nts are independent of total pressure, indicating bimolecular abstract ion processes.