BAND TERMINATION OF COLLECTIVE ROTATION - DYNAMICAL MECHANISM OF OCCURRENCE

The phenomenon of band termination of the nuclear collective rotation has been originally discussed by Bohr and Mottelson. The scenario is t he following: In the high-spin rotational nucleus, the effect of the C oriolis term produces a tendency to align the angular momenta of indiv idual single particles in a deformed rotating mean field in the direct ion of the rotation axis. This rotational alignment of the orbits of i ndividual particles tends to create a density distribution symmetric a bout the rotation axis. The band termination of collective rotation is thus expected, when the density distribution about the rotation axis becomes symmetric, with the total angular momentum being the sum of th e contributions of aligned individual particles. The main purpose of t his paper is to formulate this scenario of the band termination from t he standpoint of nuclear many-body problems and disclose the dynamical mechanism of occurrence of the band termination. It is clarified that the band termination occurs when the intrinsic state in the rotating frame cannot be stable against a variation toward an increase of the c ollective angular momentum. It is also shown that the value of the col lective angular momentum at the band termination is simply an inflecti on point of the collective rotational energy. The behavior of the sing le-particle orbitals in the rotating frame is justified and visualized to be in accordance with the scenario of Bohr and Mottelson.