Fluorescence determination of the atmospheric pollutant, NO2

A new atmospheric NO2 monitor with a detectability of 0.6 ppbv is described. A compact He-Cd 10 mW 442 nm laser excites the NO2 molecules and the resultant fluorescence is monitored by photon counting over an 80-sec integration time. The high sensitivity was achieved by development of an optimal NO2 fluorescence bandpass liquid solution filter which did not fluoresce upon absorption of scattered laser light.