Abstract
The NO3radical has been observed as a result of the flash photolysis of nitrogen dioxide under isothermal conditions (room temperature). Its concentration has been m easured together with the rate constant for the reaction NO + NO3= 2NO2. This has been found to be in quantitative agreement with previous kinetic measurements on the straight photolysis of nitrogen dioxide. The flash photolysis of nitric acid vapour under isothermal conditions also yielded NO3as an intermediate. The basis of a mechanism is reported. The NO3results from the reaction OH + HNO3= H2O + NO3, for which the rate constant has been measured.