Plane Grating Spectrometers

FIGURE 4-4. Schematic diagram of an Ebert plane grating spectrometer. 

FIGURE 4-7. Schematic diagram of a Czerny-Turner plane grating spectrometer. [Courtesy McPherson Instrument Corp.]... 

The Two-Mirror, Crossed-Beam, Plane Grating Spectrometer... 

Figure 4.1.12. Two types of NIR spectrometers (A) simple prism spectrometer and (B) Czerny-Turner plane grating spectrometer. As the prism or grating rotate, the exit sht isolates a particular wavelength interval.

Figura 3 Grating spectrometers commonly used for ICP-OES (a) monochromator, in which wavelength is scanned by rotating the grating while using a singie photomultiplier tube (PMT) detector (b) polychromator, in which each photomultiplier observes emission from a different wavelength (40 or more exit slits and PMTs can be arranged along the focal plane) and (c) spectrally segmented diode-array spectrometer.

Fig. 19. Important optical mountings for optical spectrometers with a plane (A Ebert, B Czerny-Turner) and a concave (C Seya-Namioka, D Paschen-Runge) grating, m Mirror, se entrance slit, sa exit slit, gp plane grating, gc concave grating.

Figure 11.1. Fastie-Ebert plane-grating convertible spectrograph-spectrometer. Courtesy of Jarrell Ash Division, Fisher Scientific Co.

In recent years, however, plane gratings have become almost universal in spectrometers, for the following reasons ... 

In a grating spectrometer, the interfering partial waves emitted from the different grooves of the grating all have the same amplitude. In contrast, in multiple-beam interferometers these partial waves are produced by multiple reflection at plane or curved surfaces and their amplitude decreases with increasing number of reflections. The resultant total intensity therefore differs from (4.25). 

In stigmatic spectrometers the height and width of the slit are imaged in the same plane. Several mountings (Fig. 9) are used with a plane gratings. 

Figure 9. Optical mountings for optical spectrometers with a plane grating...

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