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Number of atoms N = Number of atoms remaining at time t. N 0 = Initial number of atoms at time t = 0 N D = Number of atoms decayed at time t = + dimensionless dimensionless Decay rate, activity of a radioisotope: A = Bq = Hz = s −1 [T] −1: Decay constant: λ = /
The SI unit of mass attenuation coefficient is the square metre per kilogram (m 2 /kg). Other common units include cm 2 /g (the most common unit for X-ray mass attenuation coefficients) and L⋅g −1 ⋅cm −1 (sometimes used in solution chemistry). Mass extinction coefficient is an old term for this quantity. [1]
The absorption coefficient of a volume, denoted μ a, and the scattering coefficient of a volume, denoted μ s, are defined the same way as the attenuation coefficient. [ 6 ] The attenuation coefficient of a volume is the sum of absorption coefficient and scattering coefficients: [ 6 ]
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 ...
At small neutron flux, as in a nuclear reactor, a single neutron is captured by a nucleus. For example, when natural gold (197 Au) is irradiated by neutrons (n), the isotope 198 Au is formed in a highly excited state, and quickly decays to the ground state of 198 Au by the emission of gamma rays (𝛾). In this process, the mass number ...
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 ...
The masses of the proton and neutron are similar: for the proton it is 1.6726 × 10 −27 kg (938.27 MeV/c 2), while for the neutron it is 1.6749 × 10 −27 kg (939.57 MeV/c 2); the neutron is roughly 0.13% heavier. The similarity in mass can be explained roughly by the slight difference in masses of up quarks and down quarks composing the ...
An example is calcium-40, with 20 neutrons and 20 protons, which is the heaviest stable isotope made of the same number of protons and neutrons. Both calcium-48 and nickel -48 are doubly magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons.