Kinetic investigation of the reaction Sr(1S) + O2 + He in the temperature range from 303 to 968 K

Article abstract of DOI:10.1021/jp981998b

A kinetic study of the third-order recombination reaction Sr(¹S) + O₂ + He k₁(He)→ SrO₂ + He has been carried out in a fast-flow reactor in the temperature and pressure range of respectively 303-968 K and 6-12 Torr. Strontium atoms were generated by thermal evaporation of strontium metal pellets and then monitored by atomic absorption spectroscopy (AAS). The Arrhenius plot shows a departure from linearity above 500 K. The modified Arrhenius expression taking into account a temperature dependence of the preexponential factor for the entire temperature range results in the expression k_1Sr(He) = [(1.9 ± 0.3) × 10^-23]T^-1.7 exp-[(-12.1 ± 0.8 kJ mol^-1)/RT] cm⁶ molecule^-2 s^-1. The best representation of the temperature dependence is given by the polynomial fit log k_1Sr(He) = -60.83 + 22.44(log T) - 3.89(log T)². A lower limit to the bond energy of the SrO₂(³A₂) reaction product is estimated by means of the method based on the expression of the equilibrium constant and the theory of statistical mechanics. A value of D₀ > 244 kJ mol^-1 was obtained, which is in the range of the values derived from ab initio calculations.