Nucleus-nucleus potential, energy dissipation and mass dispersion in fusion and transfer reactions

The nucleus-nucleus potential and energy dissipation in fusion reactions are obtained from microscopic mean-field dynamics. The deduced potentials nicely reproduce the one extracted from experimental data. Energy dissipation shows a universal behaviour between different reactions. Also, the dispersion of mass distribution in transfer reaction is investigated in a stochastic mean-field dynamics. By including initial fluctuations in collective space, the description of the dispersion is much improved compared to that of mean field only. The result is consistent with the macroscopic phenomenological analysis of the experimental data.Comment: 4 pages, 4 figures. Proceedings of Second International Workshop on Compound Nuclear Reactions and Related Topics (CNR*09), October 5-8, 2009, Bordeaux, Franc

Multipole Modes for Triaxially Deformed Superfluid Nuclei

To study shape fluctuations of nuclei in transitional regions, the collective Hamiltonian method has often been employed. We intend to construct the quadrupole collective Hamiltonian with the collective inertial functions given by the local quasiparticle random-phase approximation (QRPA) based on the Skyrme energy density functional. For this purpose, we first construct a practical framework of Skyrme QRPA for triaxial nuclear shapes with the finite amplitude method (FAM). We show quadrupole strength functions for a triaxial superfluid nucleus $^{188}$Os and the Thouless-Valatin rotational moment of inertia by the local FAM-QRPA for $^{106}$Pd.Comment: 4 pages, 2 figures, accepted for publication in Proceedings of Ito International Research Center (IIRC) Symposium "Perspectives of the Physics of Nuclear Structure" (JPS Proc. Conf.

Evolution of giant monopole resonance with triaxial deformation

Background: The isoscalar giant monopole resonance (ISGMR) splits into two peaks in prolately deformed nuclei. When a nucleus is triaxially deformed, a peak appears in the middle between the two peaks. Purpose: We investigate the mechanism of the appearance of the middle peak in the ISGMR in triaxial nuclei. Method: We perform the constrained Skyrme-Hartree-Fock-Bogoliubov (CHFB) calculation for arbitrary triaxial shapes in $^{100}$Mo. We calculate the strength functions of the isoscalar monopole (ISM) and IS quadrupole modes on the CHFB states. Furthermore, we investigate vibrations of matter distributions in $x$, $y$, and $z$ directions induced by the external ISM field, with the $z$ axis being the longest axis of the triaxial shape. Results: The middle peak in the ISM strength evolves from the triaxial degree $\gamma=0^\circ$ to $60^\circ$. This is because the difference between the vibration in $x$ direction and that in $y$ direction is evident with an increase in $\gamma$ and the quadrupole $K=2$ component of the induced density of the ISM at the middle peak increases as $\gamma$ increases, where $K$ denotes the $z$ component of the angular momentum. This property is also obtained in the unperturbed ISM strength without the residual fields. Conclusions: The mixing between the monopole and quadrupole modes is primarily determined by the ground-state deformation. Therefore, the ISM strength of the middle peak becomes strong as the triaxial degree in the ground state increases.Comment: 7 pages, 7 figure

Multipole modes of excitation in triaxially deformed superfluid nuclei

Background: The five-dimensional quadrupole collective model based on energy density functionals (EDFs) has often been employed to treat long-range correlations associated with shape fluctuations in nuclei. Our goal is to derive the collective inertial functions in the collective Hamiltonian by the local quasiparticle random-phase approximation (QRPA) that correctly takes into account time-odd mean-field effects. Currently, a practical framework to perform the QRPA calculation with the modern EDFs on the (β,γ) deformation space is not available.Purpose: Toward this goal, we develop an efficient numerical method to perform the QRPA calculation on the (β,γ) deformation space based on the Skyrme EDF.Methods: We use the finite amplitude method (FAM) for the efficient calculation of QRPA strength functions for multipole external fields. We construct a computational code of FAM-QRPA in the three-dimensional Cartesian coordinate space to handle triaxially deformed superfluid nuclei.Results: We validate our new code by comparing our results with former QRPA calculations for axially symmetric nuclei. Isoscalar quadrupole strength functions in triaxial superfluid nuclei 110Ru and 190Pt are obtained within a reasonable computational cost.Conclusions: QRPA calculations for triaxially deformed superfluid nuclei based on the Skyrme EDF are achieved with the help of the FAM. This is an important step toward the microscopic calculation of collective inertial functions of the local QRPA

One-body energy dissipation in fusion reaction from mean-field theory

Information on dissipation in the entrance channel of heavy-ion collisions is extracted by macroscopic reduction procedure of Time-Dependent Hartree-Fock theory. The method gives access to a fully microscopic description of the friction coefficient associated with transfer of energy from the relative motion towards intrinsic degrees of freedom. The reduced friction coefficient exhibits a universal behavior, i.e. almost independent of systems investigated, whose order of magnitude is comparable with the calculations based on linear response theory. Similarly to nucleus-nucleus potential, especially close to the Coulomb barrier, there are sizable dynamical effects on the magnitude and form factor of friction coefficient.Comment: 7 pages, 10 figure