Interferometric spectrophotometers

Specifications of Bomem Model DA3.XX Interferometric Spectrophotometers," Tech Note 18, Bomem, Inc., 910 Place Dufour, Ville de Vanier, Quebec GIM 3B1, Canada. 

The use of data-processing equipment in conjunction with infra-red spectrophotometers, both dispersive and interferometric, produces three advantages, namely instrument control, spectrum manipulation, and spectrum identification and interpretation. Firstly, the control of the instrument is simplified and the reproducibility and accuracy of wavelength and transmission (or absorbance) are greatly enhanced. For example, one commercial Fourier transform instrument uses a helium-neon laser to obtain an accuracy of better than 0.01 cm at 4000cm, whereas older dispersive instruments could have an error of 50 cm The accuracy of... 

For thermal stability or temperature dependence measurements, the sample can be mounted in a heating stage with the possibility of exact positioning and micrometer movements. The sample used in the experiment needs to have a wedge-like shape, which enables measurements as a function of sample thickness by only moving it in the direction perpendicular to the slope, which should coincide with the director orientation. Additional requirement is an overall small thickness of the sample and moreover, the thickness needs to be known. It can best be determined by interferometric methods using a spectrophotometer. 

Figure 5 Calibration curves for the dinitrophenol herbicide DNOC in aqueous solution when using different techniques (A) PDS Photothermal deflection spectroscopy, (B) TL thermal leasing, (C) PIS Photothermal Interferometric spectroscopy, (D) PAS a photoacoustic spectroscopy, (E) a conventional spectrophotometer Cary 2400. Reproduced with permission of SPIE from Faubel W (1997) Detection of pollutants in liquids and gases. In Mandelis A and Hess P (eds) Life and Earth Sciences. Progress in Photothermal and Photoacoustic Science and Technology, Vol III, Chapter 8. Bellingham SPIE.

---