The Monochromator and Detection System

FIGURE 11. Plot of simultaneously measured SERS intensity and cathodic current versus 

FIGURE 12. Block diagram of a computer-interfaced scanning monochromator SERS instrument with photon counting detection. 

FIGURE 13. Schematic of the optics of a double monochromator. There are three slits marked SI, S2, S3 two plane gratings marked G1 and G2 four concave mirrors, Ml, M2, M5, M6 and two 45° mirrors, M3 and M4. The middle slit S2 connects the two Czerny-Turner grating monochromators and should be set slightly wider than SI and S2 to allow for different alignments in the two monochromators. 

FIGURE 14. SERS spectrum of 0.05 M piperidine in 0.1 M KCl observed from an Ag electrode after double potential step pretreatment. Full-scale sensitivity 5 x 10 counts s 488.0-nm laser excitation resolution 2 cm scan rate 50 cm min Time constant 0.5 s photon counting detection. 

FIGURE 15. Optical multichannel analyzer (OMA) SERS instrument. 

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The monochromator and detection system The monochromator for AAS does not need to have the high resolution necessary for AES, because the selectivity of AAS depends on the line width of the light source as discussed above. The role of the monochromator is to reject the majority of the background radiation as well as selecting only the pertinent HCL emission line for AAS measurements, thus monochromators for AAS have a moderate resolution of 0.02-2.0 nm. The detection system is based on a photomultiplier tube, and the readout electronics are similar to single-element AES instruments. 

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