Lidar Raman

Flame Photometry and Gas Chromatography (CyTerra) -Aerodynamic Particle Size and Shape Analysis (BIRAL) -Flow Cytometry (Luminex, LLNL) -Semiconductor-Based Ultraviolet Light (DARPA) -Polymer Fluorochrome (Echo Technology) -Laser-Induced Breakdown Spectroscopy -Raman Scattering -Infrared Absorption -Terahertz Spectroscopy -UV LIDAR... 

Amiridis V, Balis DS, Kazadzis S, Bais A, Giannakaki E, Papayannis A, Zerefos C (2005) Four-year aerosol observations with a Raman lidar at Thessaloniki, Greece, in the framework of European Aerosol Research Lidar Network (EARLINET). J Geophys Res 110 D21203. doi 10.1029/2005JD006190... 

Philbrick C.R. (2002). Overview of Raman lidar techniques for air pollution measurements in lidar remote sensing for industry and environmental monitoring. SPIE Proceedings, 4484, 136-150. 

Ultraviolet mini-Raman LIDAR for standoff, in situ identification of chemical surface contaminants has been reported [66], Using semi-portable equipment, UV Raman spectroscopic identification of bulk organic compounds at distances of over half a kilometer... 

In addition to the IR, Raman and LIBS methods previously discussed, a number of other laser-based methods for explosives detection have been developed over the years. The following section briefly describes the ultraviolet and visible (UV/vis) absorption spectra of EM and discusses the techniques of laser desorption (LD), PF with detection through resonance-enhanced multiphoton ionization (REMPI) or laser-induced fluorescence (LIF), photoacoustic spectroscopy (PAS), variations on the light ranging and detecting (LIDAR) method, and photoluminescence. Table 2 summarizes the LODs of several explosive-related compounds (ERC) and EM obtained by the techniques described in this section. 

Perrare R. A., Meffi S. H., Whiteman D. N., Evans K. D., and Leifer R. (1998a) Raman lidar measurements of aerosol extinction and backscattering 1. Methods and comparisons. J. Geophys. Res. 103, 19663-19672. 

Fig. 5. Top left Laser-induced Raman backscatter (381 nm) and two fluorescence return signals (414, 482 nm) measured during an overflight over an oleyl alcohol slick and adjacent clean sea areas bottom left the simultaneously obtained passive microwave L-band data top right same lidar sensor, Raman backscatter (381 nm) and fluorescence return signal at 500 nm during an overflight over a Murban cmde oil spill and adjacent clean sea areas bottom right same passive microwave sensor, over an artificial oil spill in the New York Bight.

With regard to the Lidar measurements, the presence of an OLA slick at the ocean surface caused a decrease in both the Raman backscatter at 381 nm and of the fluorescent bands at 414 and 482 nm, while in the presence of a thick cmde oil spill the Raman depression at 381 nm was accompanied by a simultaneous increase in the longer wavelength bands. During the same overflights a dramatic decrease in the passive microwave L-band signals was observed in the presence of an OLA slick (Blume et al. 1983), while in the presence of a cmde oil spill an increase in the same band is encountered. Unfortunately, a verification of the latter conclusions is still... 

We would like to mention one further practical application of standard Raman spectroscopy, namely the method of Raman lidar, which is now routinely used to monitor the upper atmosphere for composition (e.g. the presence of water vapour), chemical processes (e.g. the generation or depletion of ozone (O3)), and the determination of temperature profiles at high altitudes. Although absorption and fluorescence lidar systems are also widely used, Raman lidar has the distinct advantage that it is a simultaneous multispecies measurement technique, and that only a single fixed-wavelength laser is required. 

The methods most widely in use now for understanding and monitoring chemical processes that affect our environment and the atmosphere are those of TDLAS, and remote absorption/Raman spectroscopy based on lidar (absoiption-Hdar/ Raman-lidar). Application examples of these two techniques are outlined in Sections 28.1—28.3 and Sections 28.4-28.6 respectively. The chapter will conclude with the description of some less-developed techniques, which, however, provide information not easily obtained, or not accessible at all. All of them are based on ionization in one form or other, and include laser-induced breakdown spectroscopy (LIBS), matrix-assisted laser desorption ionization (MALDl) and aerosol TOFMS (ATOFMS). Examples of these are provided in Section 28.7. 

Because the cross-sections for Raman scattering are extremely small, it is used in lidar only for a few, specific applications due to its limited range and sensitivity (for one of those applications see the segment on stratospheric studies further below). 

In the Raman lidar technique, both the elastically and inelasticaUy scattered radiation contents are recorded. Elastically scattered radiation depends on both molecular and particulate species in contrast, inelastic scattering depends only on molecular scattering. The ratio of the two signals yields a parameter called the aerosol scattering ratio (ASR), which constitutes a rough measure of the concentration of aerosols. An example for an ASR measurement is shown in Figure 28.27. From the available data one can extract both the extinction and back-scattering coefficients. 

Anstnann A, Mattis I, Wandinger U, Wagner F, Reichardt J, Deshler T. 1997. Evolution of the Pinatubo aereosol Raman LIDAR observation of particle optical depth, effective radius, mass and surface area over central Europe at 53.4 N . J. Atmos. Sci. 54(22) 2630-2641. 

J. Looney, K. Petri, A. Salik Measurements of high resolution atmospheric water vapor profiles by use of a solarblind Raman lidar. Appl. Opt. 24, 104 (1985)... 

O. Uchino, M. Tokunaga, M. Maeda, Y. Miyazoe Differential absorption-lidar measurement of tropospheric ozone with excimer-Raman hybrid laser. Opt. Lett. 8, 347 (1983)... 

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