View source for Absorption edge

<font color="orange">حافة امتصاص</font> (''Ar''). <font color="blue">Arête d'absorption</font> (''Fr''). <font color="red">Absorptionskante</font> (''Ge''). <font color="black">Spigolo di assorbimento</font> (''It''). <font color="purple">吸収端</font> (''Ja''). <font color="brown">край поглощения</font> (''Ru''). <font color="green">Canto de absorción</font> (''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<sub>I</sub>'', ''L<sub>II</sub>'', ''L<sub>III</sub>'', ''etc.'' corresponding to the creation of electron holes in the 1''s'', 2''s'', 2''p''<sub>1/2</sub>, 2''p''<sub>3/2</sub> ''etc.'' atomic subshells). 

Associated with this transition is the absorption threshold (''q.v.'') characterized by the corresponding energy ''E''<sub>0</sub>.

== 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''

[[Category:X-rays]]
[[Category: X-ray absorption spectroscopy]]