Dual beam spectrometer infrared

Dougherty TP, Heilweil EJ. Dual beam subpicosecond broadband infrared spectrometer. Optics Lett 1994 19 129-131. 

Perkin-Elmer Corporation markets the PE-21 dual beam infrared spectrometer... 

Until the last twenty years, an infrared spectrometer meant a dispersive instrument this had a grating or prism to split light into its component frequencies, slits to provide the required resolution, and usually a dual sample beam to provide internal referencing of transmission. Today, Fourier transform infrared has almost completely replaced dispersive machines in the analytical laboratory. There are several reasons for this, which to be understood first require a brief introduction to the principles and technology involved. 

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