Temperature dependent study of the gas-phase kinetics of Zr(a3F2) and Hf(a3F2)

Abstract

The second-order rate constants of gas-phase Zr(a³F₂) and Hf(a³F₂) with O₂, N₂O, CO₂, NO, H₂O, SO₂ and SF₆ as a function of temperature are reported. For Zr(a³F₂), the bimolecular rate constants (in molecule^-1 cm³ s^-1) are described in Arrhenius form by k(O₂)=(2.6±0.5)×10^-10 exp(-6.2±0.7 kJ mol^-1/RT), k(N₂O)=(1.6±0.3)×10^-10 exp(-3.3±0.6 kJ mol^-1/RT), k(CO₂)=(1.4±0.2)×10^-10 exp(-5.1±0.4 kJ mol^-1/RT), k(NO)=(1.6±0.3)×10^-10 exp(-1.9±0.5 kJ mol^-1/RT) and k(SF₆)=(3.4±1.3)×10^-10 exp(-28±2 kJ mol^-1/RT), where the uncertainties are ±2σ. The rate constants for Zr reacting with H₂O and SO₂ were temperature insensitive with room-temperature rate constants of 9.1×10^-11 and 3.5×10^-10 molecule^-1 cm³ s^-1, respectively. For Hf(a³F₂), the bimolecular rate constants are described in Arrhenius form by k(O₂)=(1.2±0.1)×10^-10 exp(-2.8±0.3 kJ mol^-1/RT), k(N₂O)=(1.5±0.2)×10^-10 exp(-11.3±0.5 kJ mol^-1/RT), k(CO₂)=(1.4±0.2)×10^-10 exp(-17.5±1.2 kJ mol^-1/RT), k(H₂O)=(2.1±0.3)×10^-11 exp(-3.4±0.6 kJ mol^-1/RT), k(SF₆)=(7±5)×10^-10 exp(-41±3 kJ mol^-1/RT). The rate constants for Hf reacting with NO and SO₂ were temperature insensitive with room-temperature rate constants of 1.0×10^-10 and 3.0×10^-10 molecule^-1 cm³ s^-1, respectively. The disappearance rates for all the reactants are independent of total pressure, indicating bimolecular abstraction processes.