Infrared cutoff

These absorptions can be divided into three categories impurity absorptions due to gases or bound hydrogen isotopes, the infrared cutoff or multiphonon edge, and the fundamental structural vibrations. 

In addition to sensor QE, overall camera response of the different color channels depend upon several additional factors (1) the scene iUuminant spectral power density (2) the camera lens transmittance and (3) the infrared cutoff filter transmittance. The combined response from contributions (l)-(3) and the sensor QE is shown for a representative camera in Fig. 8. The assumed illuminant is CIE D65, with the spectral density converted from watts (per unit area per unit wavelength) to photons, so that the units cancel properly with those of the QE. The area under the green curve is highest, implying greatest sensitivity in this channel in daylight. Automatic white balance, discussed in the next section, adjusts gains to compensate for the lower areas under the red and blue curves, to yield an approximately neutral reproduction of the scene. 

Approximate low-energy cutoff for common infrared windows ... 

Fig. 11.2. Transmission of Pyrex, Vycor, and fused quartz. Transmission curves for 2-mm-lhick samples of (a) fused quariz (GE type 102), (b) Vycor (Corning 7910—note that this is a specially controlled grade the more common 7900 has an ultraviolet cutoff similar to 7740), and (c) Pyrex (Corning 7740). (Adapted from data supplied by Corning Glass Works and General I-ledlie Co.) Certain glasses and types of fused quartz are available which lack the infrared absorption at about 2.7 microns.

The cafalyst was used in aqueous suspension well mixed by means of a magnefic sfirrer. The reacting mixture was illuminated by a mercury medium-pressure lamp (t)q5e B, Helios Italquartz, Milan, Italy) coaxial with the photoreactor. A Pyrex thimble surrounding the lamp allowed the circulation of distilled water in order to cool the lamp and cutoff infrared radiation in fhese conditions fhe reactor temperature was of 295 + 2K. Lamps of 125, 500, or 1,000 W electric power were used average irradiances... 

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