Attenuation length

Short description: Particle penetration depth at which the likelihood of non-absorption is 1/e

In physics, the attenuation length or absorption length is the distance λ into a material when the probability has dropped to 1/e that a particle has not been absorbed. Alternatively, if there is a beam of particles incident on the material, the attenuation length is the distance where the intensity of the beam has dropped to 1/e, or about 63% of the particles have been stopped.

Mathematically, the probability of finding a particle at depth x into the material is calculated by the Beer–Lambert law:

P(x)=e−x/λ.

In general λ is material- and energy-dependent.

## See also

* Beer's Law
* Mean free path
* Attenuation coefficient
* Attenuation (electromagnetic radiation)
* Radiation length

## References

* S. Eidelman (2004). Particle Data Group. ed. "Review of particle physics". Phys. Lett. B 592 (1–4): 1–5. doi:10.1016/j.physletb.2004.06.001. PMID 10020536. http://pdg.lbl.gov/.
* https://web.archive.org/web/20050215215652/http://www.ct.infn.it/~rivel/Glossario/node2.html

## External links

* http://henke.lbl.gov/optical_constants/atten2.html

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