Resolution and stray light in near infrared spectroscopy.
The slit function at 1064 nm for a double monochromator spectrophotometer has been obtained with sufficient dynamic range to quantitatively account for the resolution and stray light over a wide range of resolutionv and absorbance levels. Conventional stray light tests are found to underestimate seriously that portion of the nearby stray light that most influences errors in ir absorbance determinations, and improved tests are suggested. A revision of the definition of stray light is suggested in order to minimize the variation of stray light with resolution. Convolutions of the observed slit functions with the transmittance function for the 1691-nm band of chloroform agree with observed absorbance measurements over a wide range of resolution and absorbance levels. The ratio of true to observed absorbance levels for chloroform is significantly less influenced by resolution than the literature, using triangular or Gaussian slit functions and Lorentzian absorbance functions, predicts.
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Kaye