Raman scattering instrument design

New in the market are multi-gas monitors based on the effect of Raman scattering. In the mid-1970s prototypes were established for evaluating the feasibility, which demonstrated the possibility of designing an instrument for clinical gas analysis [28]. Figure 23-30 shows the... 

Instrumentation. Because water is a weak Raman scatterer (for a review of vibrations of water molecules adsorbed on a SERS-active metal surface, see [421]) and most other electrolyte solution constituents are present only in small concentrations, standard eells with the working electrode surface close to a flat window are suitable no thin layer arrangement is required. This results in good electrode potential control and current distribution. A typical design is depicted in Fig. 5.64 for further examples and details of both the electrochemical and the spectrometric setup, see also [372]. 

This article describes the elements of Raman spectrometers for routine analyses which are available commercially. Instruments designed only for special research are not covered. Only spectrometers for classical (linear) Raman scattering are mentioned, not those for observing resonance Raman scattering (RRS), surface-enhanced Raman scattering (SERS) and all nonlinear Raman techniques they are described elsewhere in this Encyclopedia. 

In these sensors, the intrinsic absorption of the analyte is measured directly. No indicator chemistry is involved. Thus, it is more a kind of remote spectroscopy, except that the instrument comes to the sample (rather than the sample to the instrument or cuvette). Numerous geometries have been designed for plain fiber chemical sensors, all kinds of spectroscopies (from IR to mid-IR and visible to the UV from Raman to light scatter, and from fluorescence and phosphorescence intensity to the respective decay times) have been exploited, and more sophisticated methods including evanescent wave spectroscopy and surface plasmon resonance have been applied. 

In addition, special capacitor cell structures are designed to meet the requirements of some instrumental measurements (especially in situ techniques) for electrolytes. Here, we describe three types of cells used for in situ Raman, nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS) characterizations. 

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