Rate Constant Measurement of the Recombination Reaction C3H3 + C3H3

Abstract

Using the technique of infrared kinetic absorption spectroscopy, the second-order rate constant for the recombination reaction of the propargyl radical (C[sub 3]H[sub 3] + C[sub 3]H[sub 3]) has been measured and found to have the value (1.2 [+-] 0.2) x 10[sup [minus]10] cm[sup 3] molecule[sup [minus]1] s[sup [minus]1] at 295 K. The radical was produced in a flow cell by excimer laser flash photolysis ([lambda] = 193 nm) of the precursors C[sub 3]H[sub 3]Cl or C[sub 3]H[sub 3]Br and detected using time-resolved IR absorption. Absolute concentrations of C[sub 3]H[sub 3] were determined by comparing the C[sub 3]H[sub 3] absorption intensity with that of the Br atom. This calibration scheme was checked by producing methyl radicals by photolysis of methyl bromide and comparing the rate constant for methyl recombination thus obtained with literature values. The quantum yield for HCl production from the photodissociation of C[sub 3]H[sub 3]Cl at 193 nm was determined to be 0.07 [+-] 0.01. 47 refs., 10 figs., 1 tab.