Knowledge Bank

The resonance absorption technique for probing NO concentrations in the ppm range is reported. As source lamp for the emission of the $\gamma (O-O)$ band of NO, which is shown to be free from self-absorption, a hollow cathode lamp has been used operating in streaming air at low discharge current ($\sim$ 1mA). Good agreement between the observed average absorption coefficient and the calculated theoretical value is obtained. The sensitivity of the resonance absorption method is compared with continuum absorption in the UV and IR.