The first (second, ...) derivative absorption spectrum
of a molecule is defined as the first (second, ...) derivative,
of the absorbance
as a function of wavenumber,
Wavelengths may be used in place of wavenumbers but the shape of the derivative spectra
will be slightly different. When derivative spectra are obtained at low temperature,
they are called first (second, ...) derivative low temperature absorption spectra
(specifying the solvent, temperature and solute concentration).
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 1455
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook