Microscopic structure of rotational damping

Abstract

The damping of collective rotational motion is studied microscopically, making use of shell model calculations based on the cranked Nilsson deformed mean-field and on residual two-body interactions, and focusing on the shape of the gamma-gamma correlation spectra and on its systematic behavior. It is shown that the spectral shape is directly related to the damping width of collective rotation, Γ rot , and to the spreading width of many-particle many-hole configurations, Γ µ . The rotational damping width is affected by the shell structure, and is very sensitive to the position of the Fermi surface, besides mass number, spin and deformation. This produces a rich variety of features in the rotational damping phenomena. * A talk presented by M.M. at

High-lying collective rotational states in nuclei

“…Microscopic cranked shell model calculations have been performed to investigate the rotational motion at finite temperature and extract more detailed information on the transition from regular to damped regime [10]. The model, originally developed for the rare earth nucleus 168 Yb, has been successfully used to study different regions of mass and deformation [10,16]. In the case of 168 Yb, at each even spin value between I = 20h and 60h, the lowest 1000 rotational bands above yrast have been obtained by cranked shell model calculations, without including pairing.…”

“…From the discussion here presented it is clear that the extensive work made so far has indeed allowed us to make good progress in the understanding of the structure of warm nuclei. However, as discussed in section 11, there are still basic questions which are not fully answered, mainly related to the precise determination of the rotational and compound nucleus widths [16] and to a new predicted scenario, the regime of ergodic rotational bands, in which chaotic intrinsic states are combined with ordered rotational motion [17,18].…”

Rotational damping in a multi-j shell particles-rotor model

“…Recent studies on the microscopic structure and mechanism of rotational damping have been done extensively for normally deformed and superdeformed nuclei in the cranked Nilsson mean-field combined two-body residual interaction [18,19,20,21,22,23,24,25]. In these discussions, the excited rotational bands are described as intrinsic many-particle manyhole excitations in the cranking Nilsson mean-field.…”

Population and decay of superdeformed nuclei probed by discrete and quasi-continuum γ-ray spectroscopy

“…In addition to the wide smearing out of rotational energies, given by Γ rot , more narrow correlations in energy also exist for the mixed bands, forming the so called narrow component of the two dimensional strength function for consecutive transitions. The narrow component is generated by fluctuations in the transition strengths [136], it is wider than ridges stemming from unmixed bands, and it fades away with increasing excitation energy in inverse proportion to the number of basis states being mixed together, that is basically inversely proportional to the level density. For unmixed bands, the width of the first ridge is determined by the dispersion in the moment of inertia, while the width of the narrow component is roughly proportional to the compound damping width Γ comp .…”