Application of resonance Raman LIDAR for chemical species identification

BNL has been developing a remote sensing technique for the detection of atmospheric pollutants based on the phenomenon of resonance Raman LIDAR that has also incorporated a number of new techniques/technologies designed to extend it`s performance envelope. When the excitation frequency approaches an allowed electronic transition of the molecule, an enormous enhancement of the inelastic scattering cross-section can occur, often up to 2 to 4 orders-of-magnitude, and is referred to as resonance Raman (RR), since the excitation frequency is in resonance with an allowed electronic transition. Exploitation of this enhancement along with new techniques such as pattern recognition algorithms to take advantage of the spectral fingerprint and a new laser frequency modulation technique designed to suppress broadband fluorescence, referred to as Frequency modulated Excitation Raman Spectroscopy (FreMERS) and recent developments in liquid edge filter technology, for suppression of the elastic channel, all help increase the overall performance of Raman LIDAR