THERMAL-DECOMPOSITION OF CF3CL

The unimolecular decomposition CF3Cl + Kr --> CF3 + Cl + Kr has been s tudied using two different techniques, atomic resonance absorption spe ctrometry (ARAS) and laser schlieren (LS) density gradients, in two la boratories. As in our previous joint investigation of CCl4 dissociatio n, the ARAS and LS techniques give completely consistent results over the overlapping temperature range, 1800-2200 K. The title reaction is found to be fairly close to the low-pressure limit. The ARAS measureme nts between 1521 and 2173 K give k(2nd) = 1.73 x 10(-7) exp(-33837K/T) cm(3) molecule(-1) s(-1) (+/-27% at 1 sigma). This is in good agreeme nt with the earlier ARAS measurements of Kruger and Wagner. k(2nd) = 1 .15 x 10(-8) exp(-28330K/T) cm(3) molecule(-1) s(-1) (+/-20% at 1 sigm a) is obtained from the LS results between 1800 and 3000 K. The good a greement between methods verifies both the C-Cl fission path for the C F3Cl dissociation and the curve-of-growth used in the Cl atom ARAS ana lysis. RRKM analysis of these rate data indicated a larger than usual magnitude for Delta E(down), in agreement with our previous findings o n CCl4, but here it was necessary that it increase with T. The best fi t was with -[Delta E](all) = 270 cm(-1). The RRKM fit to the data is g iven by the three-parameter expression k(2nd) = 2.95 x 10(24)T(-8.50) exp(-48133K/T) cm(3) molecule(-1) s(-1) for a pressure of 300 Torr. Th is final expression agrees with both the ARAS and LS results to within +/-25% and can be used in modeling applications between 1500 and 3000 K.