Journal of Physical Chemistry, Vol.98, No.47, 12278-12283, 1994
Thermal-Decomposition of Cf3Cl
The unimolecular decomposition CF3Cl + Kr --> CF3 + Cl + Kr has been studied using two different techniques, atomic resonance absorption spectrometry (ARAS) and laser schlieren (LS) density gradients, in two laboratories. As in our previous joint investigation of CCl4 dissociation, 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 measurements 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 agreement 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 sigma) is obtained from the LS results between 1800 and 3000 K. The good agreement between methods verifies both the C-Cl fission path for the CF3Cl dissociation and the curve-of-growth used in the Cl atom ARAS analysis. RRKM analysis of these rate data indicated a larger than usual magnitude for Delta E(down), in agreement with our previous findings on CCl4, but here it was necessary that it increase with T. The best fit was with -[Delta E](all) = 270 cm(-1). The RRKM fit to the data is given 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. This 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.
Keywords:COLLISION RATE CONSTANTS;FALL-OFF RANGE;UNIMOLECULAR REACTIONS;ENERGY-TRANSFER;SHOCK-WAVES;PHOTOLYSIS;DISSOCIATION;PYROLYSIS;FLASH;TUBE