in spectrochemical analysis
The error which results if the incident beam does not fall perpendicularly to the
windows of the cell, or if the cell windows are contaminated or have some other imperfection.
PAC, 1988, 60, 1449
(Nomenclature, symbols, units and their usage in spectrochemical analysis - VII. Molecular
absorption spectroscopy, ultraviolet and visible (UV/VIS) (Recommendations 1988))
on page 1457