We describe a method for simultaneously measuring the absorption spectrum and circular dicroism (CD) of a sample in a spectrometer that employs a transparent window photomultiplier detector. During the spectral scan, the computer control system simultaneously monitors the CD signal, the high voltage applied to the detector and the current in the storage ring. A servo-control system maintains the detector current at a constant value during the scan by varying the applied high voltage. The logarithm of the photomultiplier gain is calculated from the value of the high voltage using the predetermined characteristics of the tube. The gain value is corrected for the decrease of the storage ring current with time. During a single spectral scan, the computer generates a pseudo-absorption spectrum, which is the sum of the absorbance of the sample and of various wavelength-dependent system parameters. An absolute absorption spectrum is produced when the pseudo-absorption spectrum of a "blank" sample is subtracted from the desired sample spectrum. Absorption spectra measured by this method agree with spectra obtained with a double-beam spectrophotometer.
|Original language||English (US)|
|Number of pages||5|
|Journal||Nuclear Instruments and Methods|
|State||Published - Jan 1 1981|
|Event||Proc of the Natl Conf, 2nd - Ithaca, NY, USA|
Duration: Jul 15 1981 → Jul 17 1981
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