RATE CONSTANTS (296-1700-K) FOR THE REACTIONS C2H+C2H2-]C4H2+H AND C2D+C2D2-]C4D2+D

Rate constants for the reactions C2H + C2H2 --> C4H2 + H and C2D + C2D2 --> C4D2 + D have been measured over the temperature range 296-1475 and 1226-1700 K, respectively. For the high-temperature experiments, the method was the laser photolysis-shock tube technique (LP-ST); however, for the room-temperature experiments, the laser photolysis-resonance absorption (LP-RA) technique was used. These techniques utilize the atomic resonance absorption spectroscopy (ARAS) method to monitor H or D atom formation. The results for C2H + C2H2 --> C4H2 + H may be represented by the Arrhenius expression k1H = 3.02 x 10(-10) exp(-235 K/T) cm3 molecule-1 s-1 or may be represented by the simple average of all values, k1H = (1.9 +/- 0.8) x 10(-10) cm3 molecule-1 s-1, over the temperature range 296-1475 K. The rate constant for the reaction C2D + C2D2 --> C4D2 + D can be represented by a simple average of the experimental values, k1D = (1.8 +/- 0.5) x 10(-10) cm3 molecule-1 s-1, over the temperature range 1226-1700 K. The primary quantum yield for H atom production from acetylene by single-photon absorption at 193.3 nm has also been determined to be 0.21 +/- 0.04.