arXiv subjects
Publications and source records attributed to T. Nakatsukasa.
We propose a new stochastic method to describe low-lying excited states of finite nuclei superposing multiple Slater determinants without assuming generator coordinates a priori. We examine accuracy of our method by using simple BKN interaction.
By means of the adiabatic self-consistent collective coordinate method and the pairing-plus-quadrupole interaction, we have obtained the self-consistent collective path connecting the oblate and prolate local minima in 68Se and 72Kr for the first time. The self-consistent collective path is found to run approximately along the valley connecting the oblate and prolate local minima in the collective potential energy landscape. This result of calculation clearly indicates the importance of triaxial deformation dynamics in oblate-prolate shape coexistence phenomena.
By means of the adiabatic self-consistent collective coordinate method and the pairing plus quadrupole interaction, we have obtained the selfconsistent collective path connecting the oblate and prolate local minima in 68Se for the first time. Along the collective path, the triaxial deformation parameter (gamma) changes between 0 and 60 (degree) keeping the axially symmetric deformation parameter (beta) approximately constant, indicating the importance of triaxial deformation dynamics in the oblate-prolate shape coexistence phenomena.
The adiabatic selfconsistent collective coordinate method is applied to an exactly solvable multi-O(4) model which simulates nuclear shape coexistence phenomena. Collective mass and dynamics of large amplitude collective motions in this model system are analysed, and it is shown that the method can well describe the tunneling motions through the barrier between the prolate and oblate local minima in the collective potential. Emergence of the doublet pattern is well reproduced.
An adiabatic approximation to the selfconsistent collective coordinate method is formulated in order to describe large amplitude collective motions in superconducting nuclei on the basis of the time-dependent Hartree-Fock-Bogoliubov equations of motion. The basic equations are presented in a local harmonic form which can be solved in a similar way as the quasiparticle RPA equations. The formalism guarantees the conservation of nucleon number expectation values. An extension to the multi-dimensional case is also discussed.
An experiment using the Eurogam Phase II gamma-ray spectrometer confirms the existence of an excited superdeformed (SD) band in 190Hg and its very unusual decay into the lowest SD band over 3-4 transitions. The energies and dipole character of the transitions linking the two SD bands have been firmly established. Comparisons with RPA calculations indicate that the excited SD band can be interpreted as an octupole-vibrational structure.
RPA calculations, based on the cranked shell model, are performed for superdeformed \dy\ in which five excited bands have been found recently. We show that characteristic features of the observed dynamical moments of inertia are well accounted for by explicitly taking the octupole correlations into account. Importance of the interplay between rotation and octupole vibrations is stressed, and it is suggested that one of the observed excited bands might be a collective octupole vibration built on the superdeformed yrast band.
Low-energy intrinsic $K^π$=1$^+$, $0^-$, $1^-$, $2^-$, and $3^-$ states in the even-even proton-rich Sr, Kr, and Zr nuclei are investigated using the quasiparticle random phase approximation. In the Z$\simeq$N nuclei the lowest-lying 1$^+$ states are found to carry unusually large $B(M1)$ strength. It is demonstrated that, unlike in the heavier nuclei, the octupole collectivity in the light zirconium region is small and, thus, is not directly correlated with the systematics of the lowest negative parity states.