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Mass attenuation coefficients of selected elements for X-ray photons with energies up to 250 keV. The mass attenuation coefficient, or mass narrow beam attenuation coefficient of a material is the attenuation coefficient normalized by the density of the material; that is, the attenuation per unit mass (rather than per unit of distance).
The mass attenuation coefficient can be looked up or calculated for any material and energy combination using the National Institute of Standards and Technology (NIST) databases. [ 7 ] [ 8 ] In X-ray radiography the calculation of the mean free path is more complicated, because photons are not mono-energetic, but have some distribution of ...
The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
absorption coefficient is essentially (but not quite always) synonymous with attenuation coefficient; see attenuation coefficient for details; molar absorption coefficient or molar extinction coefficient , also called molar absorptivity , is the attenuation coefficient divided by molarity (and usually multiplied by ln(10), i.e., decadic); see ...
a s = nuclear surface coefficient, a c = electrostatic interaction coefficient, a a = symmetry/asymmetry extent coefficient for the numbers of neutrons/protons,
In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm 2 for which the number of neutron-nuclei reactions taking place is equal to the product of the number of incident neutrons that would pass through the area and the number of ...
Nuclear cross sections are used in determining the nuclear reaction rate, and are governed by the reaction rate equation for a particular set of particles (usually viewed as a "beam and target" thought experiment where one particle or nucleus is the "target", which is typically at rest, and the other is treated as a "beam", which is a projectile with a given energy).
In nuclear physics, area cross-sections (e.g. σ in barns or units of 10 −24 cm 2), density mean free path (e.g. τ in grams/cm 2), and its reciprocal the mass attenuation coefficient (e.g. in cm 2 /gram) or area per nucleon are all popular, while in electron microscopy the inelastic mean free path [14] (e.g. λ in nanometers) is often ...