A nucleus is a quantum many-body system consisting of protons and neutrons, the spin and isospin of which are one half. Nuclear structures have been investigated with many kinds of probes and it has been realized that a nucleus is a quite unique system, where independent particle motions and collective motions coexist. Today, in order to understand the nucleus itself, it becomes more important to clarify microscopic structures produced by nucleons near the surface, to search various collective motions with large amplitudes and to investigate modifications of nucleon properties in the nuclear medium.
Nuclei are sensitive detectors in such interdisciplinary fields as cosmophysics and astrophysics, etc. Information on nuclear structures is indispensable to determine the detection efficiencies. We study nuclear interactions and structures with 0.01-0.4 GeV/nucleon beams obtaind by the RCNP cyclotron cascade. This energy region is most adequate to study nuclear medium and spin isospin responses. The nucleon motions associated with spins and isospins are interesting from several points of view. a. Spin isospin interactions give rise to spin isopspin gian resonances. b. The spin isospin responses are associated with pi- and rho-meson exchange interactions. c. Nuclear spin isospin interactions are relevant to axial-vector weak responses in nuclei. They are crucial for studies of nuclear responses to neutrinos.
With high quality beams and high performance detectors, these physics programs are under way, in collaboration with many physicists from all over the world.