Far-infrared spectrometers

The use of vibrational Raman spectroscopy in qualitative analysis has increased greatly since the introduction of lasers, which have replaced mercury arcs as monochromatic sources. Although a laser Raman spectrometer is more expensive than a typical infrared spectrometer used for qualitative analysis, it does have the advantage that low- and high-wavenumber vibrations can be observed with equal ease whereas in the infrared a different, far-infrared, spectrometer may be required for observations below about 400 cm. ... 

Figure 10.26. Block diagram of a far-infrared spectrometer designed for use aboard an aircraft flying at 41 000 feet [37],...

Figure 10.32. Tunable far-infrared spectrometer of Evenson [66], the so-called Tufir spectrometer. 

L Tb - elements of a spectrometer receive radiation from several radiators, including the spectrometer itself, while simultaneously acting as radiators. Thus, the balance of thermal radiation of any element in a spectrometer can be calculated, for example that of the sources, samples and detectors of near-, middle, and far-infrared spectrometers. 

Johnson et al. (2001) employed the Smithsonian astrophysical far-infrared spectrometer on seven balloon flights to measure stratospheric ozone isotopic compositions. There are two important aspects to these observations. First, they confirm and are consistent with the mass spectrometric and laboratory observations. Second,... 

Far Infrared Spectrometer System Model IR-720 Manufacturer Beckman-RIIC Ltd. 

Other groups have built tunable far-infrared spectrometers which do not involve high-frequency backward-wave oscillators. Verhoeve, Zwart, Versluis, Eirabbels, ter Meulen, Meerts, Dymanus and McLay [61] have described a system in which fixed frequency far-infrared radiation is mixed with tunable microwave radiation in Schottky barrier diodes. This instrument has been operated up to 2.7 THz, and used to study OD and N2H+. A similar system, combined with a continuous supersonic jet, has been described by Cohen, Busaiow, Laughlin, Blake, Havenith, Lee and Saykally [62]. This instrument was used to study rare gas/water clusters. 

Far-infrared spectrometers usually use a self-supporting film of polyethylene terphthalate, which has the trade name Mylar (or Melinex in Europe). The Mylar sheet has sufficient mechanical strength not... 

Figure 1 The Second Order Tunable Far Infrared Spectrometer FIR i ...

In the past, the task of building a far-infrared spectrophotometer has been undertaken independently by the research laboratories. Certainly, as a result, a number of excellent instruments have been constructed. Two of the most recent spectrometers are those built by Robinson P] at Johns Hopkins and by Yoshinaga, Oetjen, and others [ ] at Osaka. Slightly earlier, Plyler and Acquista [ ] and Lord and McCubbin [ ] constructed far-infrared spectrometers by modifying Perkin-Elmer equipment. It is a difficult and expensive project, however, and requires a sophisticated level of optical technology. 

It is possible to study rotation and restricted rotation about chemical bonds using both NMR and infrared spectroscopy. However, I think NMR has an advantage here in that the same spectrometer used for other analyses can be used for studying restricted rotation, while for infrared spectroscopy a far-infrared spectrometer would be required. I think even the experimental procedure would be simpler for NMR spectroscopy. 

In the near-infrared and midinfrared, fermanium coating on a transparent salt, such as NaCl, KBr, or Csl, is a common beam splitter material. In far-infrared spectrometers, the beam splitter is a thin film of Mylar whose thickness must be chosen for the spectral region of interest. For example, a Mylar film 0.25 mil thick can effectively cover the range from 60-375 cm. ... 

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