A kinetic investigation is presented of the reactions of ground state atomic carbon, C(2p2(3pj)), with the molecules methyl chloride, methyl bromide, methyl iodide, methyl fluoride, dichloromethane, chloroform and carbon tetrachloride. Atomic carbon was generated by the repetitive pulsed irradiation (A > ca. 160 nm) of C30 2 in the presence of excess helium buffer gas and the added reactant gases in a slow flow system, kinetically equivalent to a static system. C(23p~) was then monitored photoelectrically by time-resolved atomic resonance absorption in the vacuum ultraviolet ()t = 166 nm, 33,ยฐi ~ 23p t) with direct computer interfacing for data capture and analysis. The following absolute second-order rate constants for the reactions of C(23pj) with the above collision partners are reported (errors 2~r): Reactant kR/Cm 3 molecule 1 s-1 (300 K)
CH3CI
(4.5 + 0.3) ร 10 -12 CHaBr (5.2 _ 0.3) ร 10 -11 CH3I
(5.3 + 0.3) ร 10 -11 CH3F
(1.3 _ 0.1) ร 10-12 CH2CI 2
(5.9 + 0.3) ร 10-12 CHC13 (8.9 + 0.5) ร 10-12 CC14
(1.5 + 0.1) ร 10 -11
These yield, to the best of our knowledge, the first reported body of absolute rate data for reactions of ground state carbon with these reactants. Although a large body of absolute rate data for atomic silicon in its Si(3p2(3pj)) ground state has now been determined directly in recent years by time-resolved atomic resonance absorption spectroscopy in the ultraviolet itself with a wide range of collision partners, there are no analogous data for these particular reactants with which the data for C(23pt) may be compared. Estimates of the small energy barriers consistent with the rate data for C(23pj) + CH3C1, Br, I coupled with the bond dissociation energies of these polyatomic reactants in particular confirms the values of the bond dissociation energies for C--C1, Br, I derived from mechanistic interpretation on C 2 Swann band emission from alkali metal-organic halide diffusion flames.