Editing Internal conversion (section)

==When the process is expected==
Internal conversion is favored whenever the energy available for a gamma transition is small, and it is also the primary mode of de-excitation for 0{{sup|+}}→0{{sup|+}} (i.e. E0) transitions. The 0{{sup|+}}→0{{sup|+}} transitions occur where an excited nucleus has zero-spin and positive [[parity (physics)|parity]], and decays to a ground state which also has zero-spin and positive parity (such as all nuclides with even number of protons and neutrons). In such cases, de-excitation cannot take place by emission of a gamma ray, since this would violate conservation of angular momentum, hence other mechanisms like IC predominate. This also shows that internal conversion (contrary to its name) is not a two-step process where a gamma ray would be first emitted and then converted.

[[File:IntConvE0.jpg|thumb|Internal Conversion Coefficient for E1 transitions for Z = 40, 60, and 80 according to the tables by Sliv and Band, as a function of the transition energy.]]The competition between IC and gamma decay is quantified in the form of the '''internal conversion coefficient''' which is defined as <math>\alpha = e/{\gamma}</math> where <math>e</math> is the rate of conversion electrons and <math>\gamma</math> is the rate of gamma-ray emission observed from a decaying nucleus. For example, in the decay of the excited state at 35 keV of {{sup|125}}Te (which is produced by the decay of [[Iodine-125|{{sup|125}}I]]), 7% of decays emit energy as a gamma ray, while 93% release energy as conversion electrons. Therefore, this excited state of {{chem|125|Te}} has an IC coefficient of <math>\alpha = 93/7 = 13.3</math>.

For increasing [[atomic number]] (Z) and decreasing gamma-ray energy, IC coefficients increase. For example, calculated IC coefficients for electric dipole (E1) transitions, for Z = 40, 60, and 80, are shown in the figure.<ref>L. A. Sliv and I. M. Band, Table of Internal Conversion Coefficients, in: Alpha-, Beta- and Gamma-Ray Spectroscopy, ed. by Kai Siegbahn, North-Holland Publishing (1966), Vol. 2, Appendix</ref>

The energy of the emitted gamma ray is a precise measure of the difference in energy between the excited states of the decaying nucleus. In the case of conversion electrons, the binding energy must also be taken into account: The energy of a conversion electron is given as <math>E = (E_i - E_f)-E_B</math>, where <math>E_i</math> and <math>E_f</math> are the energies of the nucleus in its initial and final states, respectively, while <math>E_B</math> is the binding energy of the electron.