Theoretical Investigation of Isotope Separation by Using Nuclear Excitation by Electron Transition

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1. Excitation energy of the orbital electron is usually carried away by the emitted characteristic X-ray or the Auger electron. There is, however, another possibility of this energy release by exciting a nuclear state. This was pointed out by Morita theoretically long time ago, and experimentally observed in ^<189>Os. This process in named by Morita as the nuclear excitation by electron transition (in short, NEET), This can, in principle, be applied as a way of finding a very low-lying excited state of nucleus, as a method of isotope separation without using the mass difference, particularly in the case of uranium isotopes, etc.2. We have studied the atomic nuclei which are candidates to produce NEET, in isotope table.3. We have made a new theory for NEET, by assuming the one-photon exchange interaction for the electromagnetic interaction between the nucleus and electron. In this theory the magnetic multipole transitions can be taken into consideration very easily.4. Evaluation of the nuclear matrix elements can be done without using a special nuclear model, if the experimental values of the gamma-decay rates are known.5. Explicit formulas for NEET probability are obtained for the magnetic dipole and electric quadrupole transitions.6. Numerical analysis are made in the case of ^<189>Os. The magnetic dipole transition is the main component for NEET in this case.7. Since we have general formulas, we can obtain the NEET probability for any nuclides.