The N C O + N O reaction was studied by time-resolved infrared diode laser spectroscopy. The C02 + N2 channel was found to account for 56 f 7% of the total reaction rate, with N 2 0 + C O accounting for the remaining 44 f 7%. These branching ratios were found to be independent of temperature in the range 296-623 K. Furthermore, the C N + 0 2 reaction at room temperature produces C O + N O products with a yield of 23 f 10% in addition to the N C O + 0 channel, with a significant negative temperature dependence. Product energy disposal studies were also performed. C O vibration and the v3 mode of CO2 were found to account for only 0.55% and 3.4% of the available energy, respectively. These results are discussed in terms of statistical models and simple a b initio computations.

The reaction NCO + NO -products was studied at room temperature using pulsed laser photolysis with time-resolved infrared diode laser detection. C02, CO, and N20 reaction products were detected by infrared absorption under quantum-state relaxed conditions to provide absolute number densities of each species. The results indicate that three product channels are active: C02 + N2 is the most important channel, with CO + N2 + 0 and N 2 0 + CO also contributing significantly.

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The kinetics of the OH + HCNO reaction was studied. The total rate constant was measured by LIF detection of OH using two different OH precursors, both of which gave identical results. We obtain k = (2.69 +/- 0.41) x 10(-12) exp[(750.2 +/- 49.8)/T] cm(3) molecule(-1) s(-1) over the temperature range 298-386 K, with a value of k = (3.39 +/- 0.3) x 10(-11) cm(3) molecule(-1) s(-1) at 296 K. CO, H(2)CO, NO, and HNO products were detected using infrared laser absorption spectroscopy. On the basis of these measurements, we conclude that CO + H(2)NO and HNO + HCO are the major product channels, with a minor contribution from H(2)CO + NO.

The reaction of CH radicals with NO2 was studied at 296 K using multiphoton photolysis of CHBr3 at 248 nm, followed by time-resolved infrared diode laser detection of reaction products. CO, CO2, and NO were detected in significant yield, while DCN (from CDBr3), N2O, HCNO, and HNCO were formed in undetectably low yields. On the basis of consideration of product yields and secondary chemistry, we find that the major product channel is H + CO + NO or HNO + CO, which together account for 92 ± 4% of the total rate constant. HCO + NO is a minor product channel, accounting for 8 ± 4%. Upper limits are estimated for several other product channels.

Reactions Reactions H 1000Kinetics of the NCN Radical. -The kinetics of the reaction of NCN with NO are monitored using laser-induced fluorescence spectroscopy over the temperature range 298-573 K. The reaction proceeds primarily through NCNNO adduct formation as evidenced by significant pressure dependence of the rate constant. The reaction displays a negative temperature dependence typical of radical-radical reactions. Only very small amounts of N 2 O products are detected. Upper limits for the low-pressure rate constants for the reactions of NCN with O 2 , C 2 H 4 , and NO 2 are also determined.

The reaction of HCCO radicals with NO was studied at room temperature by excimer laser photolysis of ketene precursor molecules followed by infrared absorption spectroscopic detection of CO and CO 2 product molecules. After quantification of product yields and consideration of secondary chemistry, we obtain the following product branching ratios (1σ error bars) at 296 K: 0.12 ( 0.04 for CO 2 + (HCN) and 0.88 ( 0.04 for CO + (HCNO). In addition, we estimate a relative quantum yield for HCCO production in the 193 nm photolysis of CH 2 CO to be 0.17 ( 0.02.

The kinetics of the CN + HCNO reaction were studied using laser-induced fluorescence and infrared diode laser absorption spectroscopy. The total rate constant was measured to be k(T) = (3.95 +/- 0.53) x 10(-11) exp[(287.1 +/- 44.5)/T] cm3 molec(-1) s(-1), over the temperature range 298-388 K, with a value of k1 = (1.04 +/- 0.1) x 10(-10) cm3 molec(-1) s(-1) at 298 K. After detection of products and consideration of secondary chemistry, we conclude that NO + HCCN is the only major product channel.