Contents § 1. Introduction and summary 1.1. Viewpoint of cluster correlations in non-alpha-nuclei 1.2. Interactions between few-nucleon clusters 1.3. Motion of individual nucleons in molecule-like nuclei 1.4. Multi-cluster model for non-alpha-nuclei 1.5. Alpha and three-nucleon cluster states in lightest sd-shell and A=15 nuclei § 2. Interactions between few-nucleon clusters 2.1. Realistic effective nuclear potentials 2.2. N-a interaction 2.3. d-a interaction and distortion effect of deuteron 2.4. Excited states in A=4 system with 3N+N cluster model § 3. Molecular structure in the 8 Be-core region 3.1. Motion of a nucleon around a 8 Be·core 3.2. Molecular orbital model . Structure of 9 Be nucleus 3.4. Structure of 10 B nucleus 3.5. Structure of neutron-rich Be-and B-isotopes § 4. Three-cluster model of the A=lO and 11 nuclei 4.1. Orthogonality condition model § 5. 4.2. 2a + t cluster model of 11 B nucleus 4.3. 2a+d cluster model of 10 B and 10 Be nuclei 4.4. Effect of the complete antisymmetrization Alpha and three-nucleon cluster states in lightest nuclei 5.1. Structure of A=19 nuclei 5.2. Structure of A=l8 nuclei 5.3. Structure of A=l7 nuclei 5.4. Structure of A=l5 nuclei § 1. Introduction and summary sd-shell 1.1. Viewpoint of cluster correlations in non-alpha-nuclei and A=151.1.1. The light nuclei (we consider in this chapter the P-shell and lightest sd-shell nuclei) have a relatively small number of nucleons, and their characters vary remarkably from nucleus to nucleus, showing strong individuality. Even in these light nuclei we see the persistency of saturation property which is considered a fundamental property of overall nuclei. In light nuclei, the saturation property emerges through formation of the acluster as a saturating subunit. This is the fundamental aspect prescribing the characteristics of light nuclei. The basic viewpoint of a-cluster structure in light nuclei has been presented in Ref. 1). As stated in detail in the previous chapter, 2 l recent investigations on light a-nuclei 3 l~el exhibit a remarkable success of the a-cluster model, which provides us with a comprehensive understanding of nuclear structure including quite high excited states, where coexistence of the shell and cluster structures and structure change between them can be understood in a unified way. Now we naturally proceed to an extensive investigation of non-a-nuclei from the cluster-model viewpoint. 1.1.2.The structure of light nuclei has been explained mostly in terms of the intermediate-coupling shell model or the deformed shell model, like the Nilsson model and the deformed Hartree-Fock method. They assume the formation of a static one-center single-particle field. The 9 Be nucleus, on the other hand, has long been considered a prototype of the molecule-like structure of nuclei, in which two a-particles constitute a stable dumbbell-like core and a remaining (valence) neutron moves on a single-particle orbital at NERL on May 26, 2015 http://ptps.oxfordjournals.org/ Downloaded from tion, which is an "elementary interaction...

1327The nucleon-'He scattering in a wide energy region is quantitatively investigated using single channel resonating group method with the realistic effective two-body nuclear potential which includes the central, tensor and spin-orbit parts. It is shown that the empirical phase shifts and the experimental data are very well reproduced over that energy range and the N-'He elastic scattering is quantitatively understood by means of the microscopic theory with the realistic effective potential. In the p-'He scattering at high energies, an imaginary potential (volume type, surface type and non-local terms) is introduced in relation to the reaction process to the d-'He channel. Phase shifts, differential cross sections, polarizations, total cross sections and reaction cross sections are calculated at many incident energies up to 85 MeV. It is clarified that the parity and energy dependences of the nucleon-'He interaction are important to reproduce various experimental data and the tensor part of the realistic nuclear potential is mainly concerned in such properties. The odd-state part of the realistic effective nuclear potential is well determined through the analysis of the low energy phenomena of the n-'He scattering. An equivalent local potential with the parity dependence between the nucleon and 'He is also constructed.

475The nucleon-He' elastic scattering at the incident energies from 0 to 40 MeV is investigated in relation to the nuclear forces. The s-, p-, dand f-wave phase shifts are calculated by the nucleon-He4 interaction, that is constructed from an approximated Hamada and Johnston nucleon-nucleon potential. The differentia-l cross section and the polarization angular distribution calculated by these phase shifts are compared with the experimental data. We get the following results: All essential features of the nucleon-He4 scattering are explained in the energy region where the inelastic cross section is negligible. Especially the polarization at 40 MeV is fairly reproduced, which is attributed to very small (and negative) values of the d-wave phase shifts. The nucleon-He4 interaction depends drastically on the energy and the state, as the result of the presence of large non-local interaction. The nucleon-He4 spin-orbit coupling is constructed from the tensor and the spin-orbit part of the nucleon-nucleon forces. It is probable that the strength of the original spin-orbit force is rather weaker at low energies than that known from the high energy proton-proton scattering.Downloaded from *l As C2<0.l, we neglect terms proportional to C2 for the scattering problem. **l Besides V a, V T and VL8 , Hamada and Johnston's potential has a quadratic LS force, which is thought to be a phenomenological substitute for nonstatic effects of the pion theory. But we neglect this term since its effect is very small at low energies.at UNIVERSITY OF PITTSBURGH on March 11, 2015 http://ptp.oxfordjournals.org/ Downloaded from 3. b) Potential WLs(r) + WLseq (r), 3. c) Total potential WT•q(r) + WLs(r) + WLseq(r),

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