# Absorption edge

### From Online Dictionary of Crystallography

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

## 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*, *L _{I}*,

*L*,

_{II}*L*,

_{III}*etc.*corresponding to the creation of electron holes in the 122s22, 2

*s*, 2

*p*

_{1/2}, 2

*p*

_{3/2}

*etc.*atomic subshells).

Associated with this transition is the absorption threshold (*q.v.*) characterized by the corresponding energy *E*_{0}.

## Examples

For gallium: [math]\lambda_{K}[/math] = 1.1958 Ǻ; [math]\lambda_{L_{I}}[/math] = 9.5446 Ǻ; [math]\lambda_{L_{II}}[/math] = 10.8414 Ǻ; [math]\lambda_{L_{III}}[/math]= 11.1038 Ǻ.

For arsenic: [math]\lambda_{K}[/math] = 1.0448 Ǻ; [math]\lambda_{L_{I}}[/math] = 8.1195 Ǻ; [math]\lambda_{L_{II}}[/math] = 9.1187 Ǻ; [math]\lambda_{L_{III}}[/math]= 9.3617 Ǻ.

## See also

- Absorption threshold
- Fermi level
- Section 4.2.3 of
*International Tables for Crystallography, Volume C*