UV spectroscopic determination of the chlorine monoxide (ClO) = chlorine peroxide (ClOOCl) thermal equilibrium constant

摘要

The thermal equilibrium constant between the chlorine monoxide radical (ClO) and its dimer, chlorine peroxide (ClOOCl), was determined as a function of temperature between 228 and 301K in a discharge flow apparatus using broadband UV absorption spectroscopy.A third-law fit of the equilibrium values determined from the experimental data provides the expression K_(eq) = 2.16×10~(27)e~((8527±35K=T)cm~3 molecule~(-1) (1δ uncertainty).A second-law analysis of the data is in good agreement.From the slope of the van't Hoff plot in the third-law analysis, the enthalpy of formation for ClOOCl is calculated, ΔH_fo (298K) = 130:0±0:6 kJ mol~(-1).The equilibrium constant results from this study suggest that the uncertainties in Keq recommended in the most recent (year 2015) NASA JPL Data Evaluation can be significantly reduced.