Measurments of nitrous acid, nitrate radicals, formaldehyde and nitrogen dioxide for the Southern California Air Quality Study by differential optical

This paper reports that two rapid scanning (∼3000 scan min-1) differential optical absorption spectrometers were interfaced to 25 m basepath open, multiple reflection systems operated routinely at a total optical path of 800 m at Long Beach and Claremont, CA during the 1987 Southern California Air Quality Study. These instruments permitted measurements of atmospheric concentrations of nitrous acid, nitrogen dioxide and formaldehyde at the part per billion levels, and detection of the nitrate radicals with sensitivity of several tens of parts per trillion