Dispersive optical layouts

Source Dispersive device Sample Detector - Data output 

Sample Dispersive device Detector Data output 

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The double-beam system is used extensively for spectroscopic absorption studies. The individual components of the system have the same function as in the single-beam system, with one very important difference. The radiation from the source is split into two beams of approximately equal intensity using a beam splitter, shown in Fig. 2.28. One beam is termed the reference beam, the second beam, which passes through the sample, is called the sample beam. The two beams are then recombined and pass through the monochromator and slit systems to the detector. This is illustrated schematically in Fig. 2.28. In this schematic, there is a cell in the reference beam that would be identical to the cell used to hold the sample. The reference cell may be empty or it may contain the solvent used to dilute the sample, for example. This particular arrangement showing the monochromator after the sample is typical of a dispersive IR double-beam spectrophotometer. There are many commercial variations in the optical layout of double-beam systems. 

Figure 2.27 An echelle spectrometer optical layout. The eohelle grating disperses the light to a second wavelength selector, called a cross disperser. The cross disperser may be a prism or a conventional grating. [ 1993-2014 PerkinElmer, Inc. All rights reserved. Printed with permission.

Figure 2 Diagram illustrating the basic optical layout and electronic pathways for the measurement of VCD. The diagram is applicable to both dispersive VCD spectrometers and FT-IR spectrometers that use a photoelastic modulator (PEM) as the source of the polarization modulation of the light beam between left (L) and right (R) circular states.

Haseth, this describes the optical layouts of both dispersive and FT commercial spectrometers.)... 

The basic measurement layout is illustrated in Figure 2. Here radiation from an IR source is dispersed either by a diffraction grating or a Fourier-transform interferometer so that different wavelengths of the radiation can be distinguished. An infrared optical filter is placed in the beam to restrict... 

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