Absorption cross section: Difference between revisions

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Absorption cross section in the context of nuclear engineering refers to the probability of a particle (usually a neutron) being absorbed by a nucleus.

Analogously, in the context of ozone shielding of ultraviolet light, absorption cross section is the ability of a molecule to absorb a particle. Although the units are given as an area, it does not refer to an actual size area, at least partially because the density or state of the target molecule will affect the probability of absorption. Quantitatively, the number dN of particles absorbed, between the points x and x + dx along the path of a beam is the product of the number N of particles penetrating to depth x times the number n of absorbing molecules per unit volume times the absorption cross section σ:

dN/dx = –Nnσ

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 '''Absorption cross section''' in the context of [[nuclear engineering]] refers to the probability of a particle (usually a [[neutron]]) being absorbed by a nucleus.
-Analogously, in the context of [[ozone]] shielding of [[ultraviolet light]], '''absorption cross section''' is the ability of a [[molecule]] to absorb a [[photon]] of a particular [[wavelength]] and [[polarization]]. Although the units are given as an area, it does not refer to an actual size area, at least partially because the [[density]] or state of the target molecule will affect the [[probability]] of absorption. Quantitatively, the number dN of photons absorbed, between the points x and x + dx along the path of a beam is the product of the number N of photons penetrating to depth x times the number n of absorbing molecules per unit volume times the absorption cross section σ:
+Analogously, in the context of [[ozone]] shielding of [[ultraviolet light]], '''absorption cross section''' is the ability of a [[molecule]] to absorb a [[particle]]. Although the units are given as an area, it does not refer to an actual size area, at least partially because the [[density]] or state of the target molecule will affect the [[probability]] of absorption. Quantitatively, the number dN of particles absorbed, between the points x and x + dx along the path of a beam is the product of the number N of particles penetrating to depth x times the number n of absorbing molecules per unit volume times the absorption cross section σ:
 dN/dx = –Nnσ

Revision as of 14:22, 21 February 2007

See also