Quenching of Fluorescence of Small Molecules

The technique of fluorescence lidar involves detection of resonance fluorescence, and interpreting the intensity of the fluorescence signal in terms of the number of molecules being excited. A quantitative interpretation of the signal necessarily requires knowledge of the fluorescence quantum yield of the excited molecules at the ambient pressure. At stratospheric or tropospheric pressures the fluorescent yield is inversely proportional to the quenching rate for most species so that an accurate determination of species concentrations is dependent on a similarly accurate determination of the quenching rates. This is in contrast to Raman lidar where the re-emission is prompt and quenching does not play a significant role.