Attenuation length

In physics, the attenuation length or absorption length is the distance $lambda$ 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 attentuation 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 Beer-Lambert law:

:$P(x)\; =\; e^\{-x\; /lambda\}\; !,$.

In general $lambda$ is material dependent.

ee also

* Mean free path
* Attenuation coefficient
* Attenuation (electromagnetic radiation)
* Radiation length
* http://henke.lbl.gov/optical_constants/atten2.html

References

* S. Eidelman "et al." [Particle Data Group] , "Review of particle physics", Phys. Lett. B 592 (2004) (http://pdg.lbl.gov/)
* http://www.ct.infn.it/~rivel/Glossario/node2.html