KINETICS OF THE CCL3 ASSOCIATION REACTION WITH MOLECULAR-OXYGEN AT 298-K AND 333-K AND FROM 1 TO 760 TORR OF TOTAL PRESSURE

The reaction CCl3 + O2 M --> CCl3O2 + M (eq 1) was studied at 298 and 333 K as a function of pressure, from 1 to 760 Torr, using two experimental techniques. Low-pressure experiments (1-12 Torr) were carried out with the laser photolysis/photoionization mass spectrometry technique. The experiments conducted in helium at low pressure yielded rate constants that were about a factor of 2 smaller than in N2, confirming that two previous studies are in good agreement once the third body collisional efficiency of the bath gas is taken into account. High-pressure experiments (20-760 Torr) were carried out with the laser photolysis/UV absorption technique with an apparatus that is described for the first time. The value of k1 at 760 Torr and 298 K was found to be (1.65 +/- 0.12) x 10(-12) cm3 molecule-1 s-1. All the data taken with N2 as the bath gas were fitted to two different versions of the Troe expression that permits the extrapolation of fall-off data to the high- and low-pressure limiting rate constants; our results are well represented by the following forms of k0 and k(infinity): k0(T) = (6.5 +/- 0.2) X 10(-31)(T/300)-6.1 +/- 0.2 cm6 molecule 2 s-1 and k(infinity)(T) = (2.6 +/- 0.2) X 10(-12)(T/300)-1.1 +/- 0.6 cm3 molecule-1 s-1. A study of the secondary chemical reactions allowed us to determine the rate constants for the following two Br atom reactions: Br + CCl3 + M - CCl3Br + M (eq 2) and Br + CCl3O2 --> BrO + CCl3O (eq 3). At atmospheric pressure of nitrogen and 298 K, we found that k2 = (6.7 +/- 1.5) x 10(-11) cm3 molecule-1 s-1 and k3 = (6 +/- 3) x 10(-12) cm3 molecule-1 s-1. In addition, we report our spectrum of the CCl3 radical, found to have a banded structure on top of the intense, broad feature that peaks near 215 nm.