Chapter 3. Structure of the Anomalous Coupling States with Spin<i>I</i>= (<i>j</i>-1)

Abstract

Introduction 1-1 Outlz"ne53According to the j-j coupling shell model, a high-} orbit having parity opposite to that of the other orbits appears systematically in each major shell.(See Fig. 1.)When this unique-parity orbit, such as lf7i 2 and 1gt12, is filled with nucleons in odd numbers, a competition between a spin jand a spin (j-1)-state for the ground state occurs quite regularly.Such extra lowlying states with spin I=(j-1) and with unique parity have been called the anomalous coupling (AC) states.The AC states are well known as the typical phenomena which cannot be interpreted within the framework of the conventional quasi-particlephonon-coupling (QPC) theory of Kisslinger and Sorensen.!)The main purpose of this chapter*> is to introduce a new microscopic model of the AC states in the light of recent experimental developments illuminating the structure of the AC states.In the microscopic model proposed here, the AC states are regarded as typical manzfestations of the dressed three-quasi- particle (3QP) modes which have