Study of the recombination reaction CCl3+O-2 (+M) -> CCl3O2 (+M) at pressures of 2-900 bar and temperatures of 260-346 K

The recombination reaction CCl3 + O-2 (+M) --> CCl3O2 (+M) was studied in t he upper part of the falloff curve at 260, 300, and 346 K over the pressure range of 2-900 bar. CCl3 radicals were generated by photolysis of CCl3Br a t 248 nm; the temporal decay of the absorption from CCl3 at 223.5 nm was mo nitored in the presence of O-2; falloff curves of the rate constants were d etermined in N-2 and He as bath gases. The falloff curves could well be rep resented by limiting high-pressure rate constants k(infinity) = (5.2 +/- 0. 2) x 10(-12) (T/300 K)(-1.4 +/-0.4) cm(3) molecule(-1) s(-1) from the prese nt work, limiting low-pressure rate constants k(0) = [N-2] (1.1 +/- 0.3) x 10(-30) (T/300 K)(-6.3 +/-1.0) cm(3) molecule(-1) s(-1) or k(0) [He] (4.2 /- 0.7) x 10(-31) (T/300 K)(-6.9 +/-1.0) cm(3) molecule(-1) s(-1) from the literature, and center-broadening factors F-c (N-2) = (0.35 +/- 0.03) (T/30 0 K)(-0.35) or F-c (He) (0.30 +/- 0.03) (T/300 K)(-0.48) derived from unimo lecular rate theory. An onset of diffusion-controlled kinetics at pressures above about 300 bar of N-2 was observed, in agreement with predictions fro m simple diffusion models. The derived rate constants are analyzed in the f ramework of unimolecular rate theory.