Frontiers Of The Nuclear Shell Model

摘要

I shall first discuss the variations of magic numbers and shell structure in exotic nuclei by using effective single-particle energies. An origin of these variations is shown to be the spin-isospin dependent part of the nucleon-nucleon interaction in nuclei. Such variations can be referred to as the shell evolution. As an outcome of this shell evolution in neutron-rich exotic nuclei, magic numbers such as N=8, 20, etc. can disappear, while N=6, 16, etc. arise. The shell gap is changed as a consequence of the shell evolution, and a good example is shown for ~(30)Na. An interesting case regarding shapes of exotic nuclei is presented for excitation energies and B(E2) values of ~(32,34)Mg exotic nuclei. It is suggested that various anomalous properties of exotic nuclei can be studied with the paradigm of shell evolution. In the second part, recent results of shell-model studies will be presented for some Sn and Te nuclei. The anomalous B(E2) value of ~(136)Te can be explained within the shell model description which has described the spherical-to-deformed phase transition in Ba isotopes.