화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.104, No.27, 6406-6410, 2000
Kinetic study of the reactions of Ca(S-1) and Sr(S-1) atoms with Cl-2 in the temperature ranges from respectively 303-1038 K and 303-991 K
A kinetic investigation of the second-order reactions Ca(S-1) + Cl-2((1)Sigma(g)(+)) --> (k(1Ca)) CaCl + Cl and Sr(S-1) + Cl-2((1)Sigma(g)(+)) --> (k(1Sr)) SrCl + Cl was carried out in a fast-flow reactor in the temperature ranges of respectively 303-1038 K and 303-991 K. The calcium and strontium atoms in the gas phase were generated by thermal evaporation of the solid metal pellets. The concentration of the gas-phase metal atoms was followed by means of atomic absorption spectroscopy (AAS) at wavelengths of 422.7 nm for calcium and 460.7 nm for strontium atoms. Both reactions show an Arrhenius behavior and the rate constants are given by k(1Ca) = [(6.0 +/- 0.8) x 10(-10)]exp(-0.2 +/- 0.5 kJ mol(-1)/RT)cm(3) molecule(-1) s(-1) and k(1Sr) = [(7.3 +/- 0.6) x 10(-10)]exp(-0.4 +/- 0.4 kJ mol(-1)/RT)cm(3) molecule(-1) s(-1). The results are interpreted in terms of the electron-jump mechanism. For both the Ca/Cl-2 and the Sr/Cl-2 reactions, the experimental rate constants are too high to be quantitatively explained by the classical electron-jump mechanism. However, the modified electron-jump mechanism which takes into account long distance forces between the reagents gives a better agreement with the experimental values.