Spectrophotometer monochromator

Fig. 10.2 Scheme of the microcomputer used to control a spectrophotometer monochromator. (Reproduced from [5] with permission of Taylor Francis). 

Quartz also has modest but important uses in optical appHcations, primarily as prisms. Its dispersion makes it useful in monochromators for spectrophotometers in the region of 0.16—3.5 m. Specially prepared optical-quality synthetic quartz is requited because ordinary synthetic quartz is usually not of good enough quality for such uses, mainly owing to scattering and absorption at 2.6 p.m associated with hydroxide in the lattice. 

Some commercial spectrophotometers have fluorescence attachments which allow the sample to be irradiated from an ancillary source and the resulting fluoresence to pass through the monochromator for spectral analysis. 

Fig. 19.2 Layout of an infrared spectrophotometer employing a diffraction grating for monochromation. Reproduced by permission from R. C. J. Osland, Principles and Practices of Infrared Spectroscopy, 2nd edn, Philips Ltd, 1985.

In a simple flame (emission) photometer an interference filter (Section 17.7) can be used. In more sophisticated flame emission spectrophotometers which require better isolation of the emitted frequency, a prism or a grating monochromator is employed. 

In the spectrophotometer, the crystal may be placed between source and sample, in which case it acts as a monochromator. Or, it may be inserted between sample and detector, where it acts as an analyzer of the transmitted beam. 

Flame photometer or spectrophotometer incorporating nebulizer and burner, filters, prism or grating monochromator, photocell or photomultiplier detection system. 

Filter-photometer or spectrophotometer incorporating prism or grating monochromator, phototube photomultiplier or diode array, glass, quartz or plastic cells. 

Some spectrophotometers are single-beam instruments, and some are double-beam instruments. In a double-beam instrument the light beam emerging from the monochromator is split into two beams at some point between the monochromator and the detector. The double-beam design provides certain advantages that we will discuss shortly. 

The infrared spectrophotometers are based on either single monochromation or double monochromation ... 

The schematic layout of a single-monochromator infrared spectrophotometer has been duly depicted in Figure 22.2. 

Figure 22.2. Optical Diagram of a Single-Monochromator Infrared Spectrophotometer.

Figure 22.3 Optical Diagram of a Double-Monochromator Infrared Spectrophotometer (Beckman Model IR-9)...

The various components of a double-monochromator infrared spectrophotometer shown in Figure 22.3 are as follows below ... 

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