Molecular‐modulation spectrometry: CH3ONO photolysis and detection of nitroxyl

The method of molecular‐modulation spectrometry for studying photochemical reactions has been applied to methyl nitrite photolysis. The infrared absorption of the nitroxyl radical HNO has been observed in the gas phase at 3300 cm−1. Under the present experimental conditions the steady‐state concentration of HNO under steady illumination was 1.1 × 1012 particles/cc, and the observed modulation amplitude was 4.5 × 1010 particles/cc. At 25°C and 1 atm of nitrogen, the cross section for infrared absorption by HNO at 3300 cm−1 is 1.7 × 10−19 cm2. The rate constant ratio b/c equation image was found to be 8.0. From the literature value of the rate constant d equation image , the observed rate constant for the reaction equation image is e = (5 ± 1) × 10−11 cc/particle sec.