Application of the Chemiluminescence Method to the Determination of Total Photochemical Activity of Hydrocarbons

A method for the determination of the total photochemical activity of hydrocarbons has been investigated. The electric discharge was carried out in O2/He gas to produce atomic oxygens using a 2450 MHz microwave generator. The discharged gas was introduced into a chemiluminescence reactor through an orifice, and made to react with hydrocarbon gases. A. monochromator, a photomultiplier tube cooled thermoelectrically, and a photon counting systern were employed to measure the intensity of the chemiluminescence. The typical operating conditions suitable for the measurement of the total photochemical activities were as follows: O2 concentration of discharged gas (O2/He) 1.0%, flow rate of discharged gas: 100 cm3. min-1 flow rate of hydrocarbon gas: 60cm3imin-1, pressure at discharged section: 10 Tom pressure at chemiluminescence section: 1.5 Torr, the microwave output: 15 W. Active species such as OH, O, HO2, and O3 are known to play an important role in the process of the smog formation. Both OH and O are noted because of their remarkable reactivities with hydrocarbons, and a search is made for the ralationship between the rate constants in the reactions of the hydrocarbons with these species. It is proposed that the photochemical reactivities of the hydrocarbons may be represented by the reaction of O atoms with hydrocarbons. The. photochemical activities were obtained by the measurement of OH emission intensity at 3089Å from the reaction. Examination of the relationship between the rate constant and the emission intensity indicates, in the case of [O]δt0.7