Studies on nuclear resonant scattering of synchrotron radiation by 40K

The studies on nuclear resonant scattering by K-40 using synchrotron radiation are reviewed. Brilliant and high pure synchrotron radiation permitted us to observe the nuclear resonant forward scattering by K-40 in a powdered KCl sample, the excitation of which is impossible with ordinary radioactive sources. Furthermore, nuclear resonant inelastic scattering of synchrotron radiation by K-40 in the KCl sample at room temperature has been measured using a high-resolution monochromator. Adding to these, from the excitation experiments of K-40, the energy and lifetime of the first excited state of K-40 were confirmed. These measurements clearly show that the studies on the electronic states through hyperfine interactions and the dynamical properties of potassium atoms, which are very important in material science and biology, are possible. It should be noted that K-40 is the natural isotope of potassium and weakly radioactive. Our observation of forward and inelastic scattering of the radioactive nuclide K-40 will lead to further studies on other radioactive nuclides the resonant forward and inelastic scattering of which are not observed to date.