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Abstract:
The thermal dissociation reaction CF3 (+ Ar) → CF2 + F (+ Ar) was studied in incident and reflected shock waves by monitoring UV absorption signals of the primary dissociation product CF2. CF3 radicals were produced by thermal decomposition of CF3I. Accounting for secondary reactions of F atoms, rate constants for the unimolecular dissociation were derived. Experimental parts of the falloff curves were obtained over the ranges 1544 - 2106 K and 1.0×〖10〗^(-5)≤["Ar" ]≤9.3×〖10〗^(-5 ) "mol " 〖"cm" 〗^"-3" . Theoretical modelling allowed for a construction of the full falloff curves connecting the limiting low pressure rate constants k_0=["Ar" ] 2.5×〖10〗^18 (T⁄(2000 "K" ))^(-5.1) " exp" ((-42450 "K" )⁄T) 〖"cm" 〗^"3" 〖"mol" 〗^(-1) "s" ^(-1) with the limiting high pressure rate constants k_∞= 1.6×〖10〗^16 (T⁄(2000 "K" ))^(-1.3) "exp" ((-43250 "K" )⁄T) "s" ^(-1) (center broadening factors of F_cent= 0.25, 0.22, and 0.20 at 1500, 2000, and 2500 K, respectively, were used). The influence of simplifications of falloff expressions and of limiting rate constants on the representation of experimental data is discussed.
