Characteristics diffuse transmittances

There are basically two types of spectrophotometers that differ by position of the monochromator with respect to the sample. Sample illumination is either monochromatic or polychromatic. Each has its own characteristic response to fluorescent materials. Measurement data from both types of spectrophotometers are presented here. The ideal type of instrument for fluorescent samples would use both monochromatic illumination and monochromatic detection. The design is difficult to realize in practice, especially with respect to diffuse transmittance measurements and integrating spheres. 

Optical fibres can be used in the transmittance and ATR mode (a special ATR application is the remote sensor), and even in the reflectance mode. The development of special optical fibres for transmission, transflection or diffuse reflectance measurements favours on-line analysis of problematic product streams and reaction mixtures (solutions, suspensions, emulsions, melts, solids). Both quartz and fluoride (ZrF4-based) glass fibres are used, with the former having poor transmission characteristics above 2000 nm. 

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