post-filter effect

in luminescence spectroscopy
This effect arises when the exciting beam does not fill the cell completely and luminescence is absorbed by the analyte and interfering impurities in the non-illuminated region facing the detector.
PAC, 1984, 56, 231. 'Nomenclature, symbols, units and their usage in spectrochemical analysis-Part VI: molecular luminescence spectroscopy' on page 244 (