Absorption edge

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Discontinuité, arête d'absorption (Fr). Absorptionskante (Ge). Canto de absorción (Sp). край поглощения (Ru). Spigolo di assorbimento (It). 吸収端 (Ja)

Definition

An absorption edge is the energy at which there is a sharp rise (discontinuity) in the (linear) absorption coefficient of X-rays by an element, which occurs when the energy of the photon corresponds to the energy of a shell of the atom (K, LI, LII, LIII, etc. corresponding to the creation of electron holes in the 122s22, 2s, 2p1/2, 2p3/2 etc. atomic subshells).

Associated with this transition is the absorption threshold (q.v.) characterized by the corresponding energy E0.

Examples

For gallium: λK = 1.1958 Ǻ; \lambda_{L_{I}} = 9.5446 Ǻ; \lambda_{L_{II}} = 10.8414 Ǻ; \lambda_{L_{III}}= 11.1038 Ǻ;

For arsenic: λK = 1.0448 Ǻ; \lambda_{L_{I}} = 8.1195 Ǻ; \lambda_{L_{II}} = 9.1187 Ǻ; \lambda_{L_{III}}= 9.3617 Ǻ;

See also