AbstractThe thermal decomposition of CCl3O2NO2,CCl2FO2NO2, and CClF2O2NO2was studied in a temperature‐controlled 420 l reaction chamber usingin situdetection of peroxynitrates by long‐path IR absorption. The temperature dependence of the unimolecular dissociation rate constants was determined at total pressures of 10 and 800 mbar in nitrogen as buffer gas, and the pressure dependence was measured at 273 K between 10 and 800 mbar. In Troe's notation, the data are represented by the following values for the limiting low and high pressure rate constantsk0/[N2] andk∞and the fall‐off curvature parameterFc(in units of cm3molecule−1s−1, s−1): CCl3O2NO2,k0/[N2] = 6.3 × 10−3exp(−85.1 kJ · mol−1/RT),k∞= 4.8 × 1016exp(−98.3 kJ · mol−1/RT),Fc= 0.22; CCl2FO2NO2,k0/[N2] = 1.01× 10−2exp(−90.3 kJ · mol−1/RT),k∞= 6.6 × 1016exp(−101.8 kJ · mol−1/RT),Fc= 0.28; and CClF2O2NO2,k0/[N2] = 1.80 × 10−3exp(−87.3 kJ · mol−1/RT),k∞= 1.60 × 1016exp(−99.7 kJ · mol−1/RT),Fc= 0.30. From these dissociation rate constants and recently measured rate constants for the reverse reaction (see Caralp, Lesclaux, Rayez, Rayez, and Forst [19]), bond energies (=ΔH r,00) of 100, 103, and 104 kJ/mol were derived for the RO2–NO2bonds in CCl3O2NO2, CCl2FO2NO2, and CClF2O2NO2, respectively. The kinetic and thermochemical parameters of these decomposition reactions are compared with those of the dissociation of other peroxynitrates. Atmospheric implications of the thermal st