Journal of Physical Chemistry A vol:102 issue:43 pages:8333-8338
A kinetic study of the third-order recombination reaction Sr(S-1) + O-2 + 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) x 10(-23)]T-1.7 exp[(-12.1 +/- 0.8 kJ mol(-1))/RT] cm(6) molecule(-2) s(-1). The bl:st 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((3)A(2)) 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 D-0 > 244 kJ mol(-1) was obtained, which is in the range of the values derived from ab initio calculations.