Beam-splitter and cell-window errors in fluorescence spectrometry

Fluorescence excitation spectra should be corrected for distortions caused by spectral variations in the transmittance/reflectance ratio of the beam splitter and by variations in the transmittance of cell windows. The polarization of the excitation beam may cause a large uncertainty in the beam-splitter correction, but this source of error can be eliminated by using angles of incidence of 15 degrees , or less, at the beam splitter. The small distortions due to the transmittances of the sample-cell and quantum-counter entrance windows can be made to cancel one another it the angle of incidence at the quantum counter is also 15 degrees or smaller.