Sample Illumination and Light Collection

Sample illumination and methods for collecting Raman scattered light can be subdivided into three groups the use of conventional optics like lenses and mirrors, the use of fiber optics, and the use of optical microscopes. 

A comprehensive overview of cells and sample illumination methods in Raman spectroscopy is given in [29]. Rectangular cells, spherical cells, NMR tubes or light pipes may be used. The most popular arrangements for sample illumination are shown in Fig. 6.11. 

Optical fibers are increasingly used for remote Raman probing, for example to monitor chemical processes in-line or inside a reactor. The laser beam is guided to the probe head by an excitation fiber, and the Raman signal is returned to the detector by a collection fiber. Probe heads usually work in the 180° arrangement. There are two different types of fiber probes for common use in Raman spectroscopy the concentric unfiltered fiber bundle and the filtered probe. The fiber bun- 

Reference Data Table 2 Method Parameter Reference Sheet 

Required User Skills Unskilled for routine measurements 

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Figure 8. Sample illumination and light collection geometry to record vibrationally resolved fluorescence spectra of a single molecule. The sample is attached to the optical flber. S sample, P paraboloidal collection mirror, M flat mirror, BS beam splitter, F long pass filter, L lens, PMT photomultiplier tube, CCD charge-coupled device detector (after Ref 38).

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