Dispersive element Echelle monochromator

FIGURE 7-23 An echelle monochromator (a) arrangement of dispersing elements, and (b) schematic end-on view of the dispersed radiation from the point of view of the transducer. 

A conventional monochromator (either Ebert, Czerny-Turner, Littrow or Echelle) may be used (see AAS sections for details), but some of the more basic instrumentation uses interference filters. These are optical filters that remove large bands of radiation in a nondispersive way. A dispersion element such as a prism or a grating is therefore not required. Only a relatively narrow band of radiation is allowed to pass to the detector. The disadvantage with such devices is that they are not particularly efficient and hence much of the fluoresced light is lost. An alternative development is the multi-reflectance filter. This is shown diagramatically in Figure 3, and has the... 

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