Page "Atomic absorption spectroscopy" Paragraph 48

The relatively small number of atomic absorption lines ( compared to atomic emission lines ) and their narrow width ( a few pm ) make spectral overlap rare ; there are only very few examples known that an absorption line from one element will overlap with another.

Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line.

This kind of absorption might be caused by un-dissociated molecules of concomitant elements of the sample or by flame gases.

We have to distinguish between the spectra of di-atomic molecules, which exhibit a pronounced fine structure, and those of larger ( usually tri-atomic ) molecules that don ’ t show such fine structure.

Another source of background absorption, particularly in ET AAS, is scattering of the primary radiation at particles that are generated in the atomization stage, when the matrix could not be removed sufficiently in the pyrolysis stage.