RATE-CONSTANT MEASUREMENT OF THE RECOMBINATION REACTION C3H3+C3H3

Using the technique of infrared kinetic absorption spectroscopy, the s econd-order rate constant for the recombination reaction of the propar gyl radical (C3H3 + C3H3) has been measured and found to have the valu e (1.2 +/- 0.2) x 10(-10) cm(3) molecule(-1) s(-1) at 295 K. The radic al was produced in a flow cell by excimer laser flash photolysis (h = 193 nm) of the precursors C3H3Cl or C3H3Br and detected using time-res olved IR absorption. Absolute concentrations of C3H3 were determined b y comparing the C3H3 absorption intensity with that of the Br atom. Th is calibration scheme was checked by producing methyl radicals by phot olysis of methyl bromide and comparing the rate constant for methyl re combination thus obtained with literature values. The quantum yield fo r HCl production from the photodissociation of C3H3CI at 193 nm was de termined to be 0.07 +/- 0.01.