Internal conversion coefficient
Encyclopedia
In nuclear physics
, the internal conversion coefficient describes the rate of internal conversion
.
The internal conversion coefficient may be empirically determined by the following formula:
There is no valid formulation for an equivalent concept for E0 (electric monopole) nuclear transitions.
There are theoretical calculations that can be used to derive internal conversion coefficients. Their accuracy is not generally under dispute, but it should be understood that since they depend on quantum mechanical models involving purely electromagnetic interactions between nuclei
and electron
s, there may be unforeseen effects which result in a conversion coefficient differing from one that is empirically determined.
Internal conversion coefficients can be looked up from tables, but this is time-consuming. Computer programs have been developed (see the ICC Program) which will present internal conversion coefficients quickly and easily.
The three theoretical calculations of interest are the Rösel, Hager-Seltzer, and the Band.
The Hager-Seltzer calculations omit the M and higher-energy shells on the grounds (usually valid) that those orbitals have little electron density at the nucleus and can be neglected. To first approximation this assumption is valid, upon comparing several internal conversion coefficients for different isotope
s for transitions of about 100 keV.
The Band calculation assumes that the M shell may contribute to internal conversion to a non-negligible extent, and incorporates a general term (called "N+") which takes into account the small effect of any higher shells there may be, while the Rösel calculation works like the Band, but does not assume that all shells contribute and so generally terminates at the N shell.
Nuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
, the internal conversion coefficient describes the rate of internal conversion
Internal conversion
Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower atomic orbitals, causing the electron to be emitted from the atom. Thus, in an internal conversion process, a high-energy electron is emitted from the radioactive atom, but...
.
The internal conversion coefficient may be empirically determined by the following formula:
There is no valid formulation for an equivalent concept for E0 (electric monopole) nuclear transitions.
There are theoretical calculations that can be used to derive internal conversion coefficients. Their accuracy is not generally under dispute, but it should be understood that since they depend on quantum mechanical models involving purely electromagnetic interactions between nuclei
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
and electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s, there may be unforeseen effects which result in a conversion coefficient differing from one that is empirically determined.
Internal conversion coefficients can be looked up from tables, but this is time-consuming. Computer programs have been developed (see the ICC Program) which will present internal conversion coefficients quickly and easily.
The three theoretical calculations of interest are the Rösel, Hager-Seltzer, and the Band.
The Hager-Seltzer calculations omit the M and higher-energy shells on the grounds (usually valid) that those orbitals have little electron density at the nucleus and can be neglected. To first approximation this assumption is valid, upon comparing several internal conversion coefficients for different isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s for transitions of about 100 keV.
The Band calculation assumes that the M shell may contribute to internal conversion to a non-negligible extent, and incorporates a general term (called "N+") which takes into account the small effect of any higher shells there may be, while the Rösel calculation works like the Band, but does not assume that all shells contribute and so generally terminates at the N shell.
External links
- Nuclear Structure and Decay Data - IAEA with query on Conversion Coefficients