The method described previously has been used to convert a conventional monochromator to a quadruple monochromator having much higher resolving power and giving almost complete elimination of scattered radiation. A pair of right-angled mirrors, placed so that the planes in which they lie intersect at the entrance slit, reflects the radiation through the dispersing system several times before passing through the exit slit. Radiation of different orders, and consequently of different wavelengths, passes through the exit slit simultaneously. A chopper is so arranged that only one of these orders, in the present work the fourth, is interrupted. An amplifier tuned to the same frequency as the chopper is used to amplify the signal from the detector, thereby ensuring that only fourth-order radiation gives an output signal. The method is also applicable to the construction of higher order monochromators. The conversion of a Perkin-Elmer infrared spectrometer (Model 12C) to a quadruple monochromator is described and the performance of the instrument is illustrated by typical spectra recorded over the range 3–20μ.
© 1952 Optical Society of AmericaFull Article | PDF Article
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