Single monochromator

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.

The optical train affords as much as twice the dispersion and the ultimate resolution is fairly comparable to any single-monochromator instrument (Figure 22.2),... 

The addition of a single monochromating crystal gives the device great flexibil ity, since one has independent control over the collimation, by the number of reflections, and the bandpass, controlled by the width of the reflection of the monochromating crystal. Figure 2.16 shows one variant, a three-reflection... 

Bais A. F., C. S. Zerefos and C. T. McElroy (1996) Solar UVB Measurements with the Double- and Single-monochromator Brewer Ozone Spectrophotometers, Geophys. Res Lett. 23, S33-836. 

For photostability testing purpose the small, single monochromator computer driven units are more than adequate. Slightly more expensive than a photometer/ radiometer combination, these units can measure the complete spectrum on a realtime basis and output the results in several different formats. When coupled with the computer software available as part of most packages it should be the measurement system of choice. Chapter 13 of this book discusses these instruments in more detail. 

Spectroradiometers, often dual-monochromator spectrophotometers, allow for the rapid measurement of all wavelengths that are used for obtaining SPDs. Several single monochromator spectroradiometers are also available on the market. These units are less expensive, smaller, of lesser resolution, and have higher amounts of stray light (Table 1) but are sufficient for most pharmaceutical photostability purposes. 

Raman spectra have been obtained with a Jobin Yvon single monochromator equipped with a notch filter and a CCD detector cooled at liquid nitrogen temperature. Raman scattering has been excited through a He-Ne laser (632.8 nm) at low power (6 mW) to avoid heating effects. Spectra have been taken both in situ, that is during and after the deposition in an ultra high vacuum (UHV) chamber, and ex situ after the exposition of the deposited film to atmosphere. 

Small, efficient single monochromators based on concave holographic gratings, transmission holographic gratings or standard Czemy-Turner monochromators in combination with a notch filter. 

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