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In photon activation analysis (PAA), nuclides of the analyte elements in the material sample under study are converted to radioactive nuclides through exposure to high‐energy photons. Characteristic radiation upon disintegration of these radionuclides (preferably γ quanta) is then measured with appropriate spectrometers. PAA is not an “absolute” method; hence, the samples under investigation have to be irradiated together with a comparative material sample (calibration material) with well‐known chemical composition. After spectroscopic measurement of both samples, the quantitative evaluation is performed by comparison of the two resulting element spectra, basically following the same procedure as in most instrumental methods, e.g. ICP, AAS, etc. The particular advantages of this method are freedom from blank values; reduced danger of contamination; and, since frequent investigations can be carried out “nondestructively”, easy handling of materials that are difficult to treat chemically, e.g. certain refractory metals, dusts, ashes, etc. Another advantage is the option to study very small samples (a few milligrams) as well as very large ones (up to kilogram amounts). Basically, there are no limitations concerning the nature of material studied but matrices like lead or other heavy elements raise the limit of detection considerably, and separation techniques have to be used.

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