Continuous (in the wavelength
, not time sense) radiation
arising for example from non-quantized free-free transitions of electrons in the fields of the ions, free-bound transitions or radiative recombinations of electrons and ions, incandescent radiation emitted by hot solids (when the radiation distribution conforms to that described by Planck's law, it is considered black-body radiation) and unresolvable band spectra
, i.e. where the spectral lines are wider than the spacings between them.
PAC, 1985, 57, 1453
(Nomenclature, symbols, units and their usage in spectrochemical analysis - V: Radiation sources (Recommendations 1985))
on page 1462
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. doi:10.1351/goldbook