Radionuclides gamma transitions

Adams, F. and Dams, R. (1969). A compilation of precisely determined gamma-transition energies of radionuclides produced by reactor irradiation. J. Radioanal. Chem. 3, 99. 

The parent radionuclide decays by several yS-particle transitions (two shown), producing metastable Tc with 87.5% intensity, while 12.5% decay directly to long-lived Tc. Subsequently, metastable Tc decays by isomeric transition to Tc with a half-life of 6.02 h and emission of 140.5 keV gamma radiation. Tc decays with a half-life of 212000 years to stable ruthenium-99 (Boyd 1982). 

The state-to-state transition energy for gamma-ray emission ranges from a few kiloelectron volts to generally less than 3 MeV. The energy of the gamma ray is dictated by the nuclear structure of the emitting radionuclide, and thus is characteristic of that radionuclide. 

Each radionuclide among the more than one thousand that are known has a unique decay scheme by which it is identified. For this reason, among others, researchers have studied decay schemes over the years and their reported information has been compiled and periodically updated. The compiler surveys the reported information for each radionuclide and attempts to select the most reliable information for constructing a self-consistent decay scheme. The fraction of beta particles that feed an excited state must match the fraction of gamma rays plus conversion electrons emitted by the excited state. The energy difference between any two states must be consistent with the energies of the transition radiations plus the recoil energy of the atom that emitted the radiations. 

Calibration curves for this method were constructed by use of single beta transitions only. Further tests of the method were necessary to determine the usefulness of the procedure for measurement of samples that contain radionuclides that emit X-rays, gamma rays, auger and compton electrons, and alpha particles. Table 1 compares those efficiencies predicted from the channels ratio calibration curves with the actual counting efficiencies for several radionuclides which decay by various means. Efficiencies obtained by counting with the wide-beta counter are listed for comparison. The predicted results are in good agreement with the actual efficiencies except in the case of and to a lesser... 

Gamma rays—High-energy electromagnetic radiation emitted by certain radionuclides when their nuclei transition from a higher to a lower energy state, very similar to x-rays. 

The radionuclides of principal significance in contamination buildup, their origins and their production reactions are summarized in Table 4.2. These radionuclides are all gamma emitters with a comparatively long halflife. In virtually all plants, the radiation dose rates in the area surrounding the circuits and components are predominantly due to °Co, because of the high energies of its y quants of 1.17 and 1.33 MeV and the transition probability of both of them of 100%. Besides Co, additional activation products of other constituents of austenitic steels and nickel-based alloys, in particular Co, have to be mentioned. Only in special cases... 

Gamma (y) rays are photons deriving from isomeric transitions. Isomeric transitions occur when a nucleus remains in an excited state after a particle emission or a decay by electron capture. These intermediate levels are referred to as isomeric states (or metastable states), and each decays to a lower state (either the ground state or another intermediate state) with lifetimes from picoseconds to years. Gamma ray emissions are characteristic of the radionuclide, and the energies of the emitted photons depend on the energy differences between the initial excited state and the next one. 

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