Theory of fission-mass distributions demonstrated for 226Ra, 236U, 258Fm

With the mass asymmetry described by the dynamical collective fragmentation coordinate ξ, and with use of the asymmetric two-center shell model, the fission mass distributions for 226Ra, 236U, and 258Fm (which are typical representatives for triple-, double-, and single-humped distributions) are explained

Collective effects on mass asymmetry in fission

the development of the mass asymmetry vibrations in the final stages of the fission process is studied with an approximate treatment of the coupling to relative motion. A parametrized friction is introduced and its effects are studied. Numerical results are presented for 236U, together with estimates for the kinetic energy of the fragments. RADIOACTIVITY, FISSION 236U; calculated mass distribution, kinetic energy distribution. Collective dynamics, shell correction method, cranking model

Collective sideward flow of nuclear matter in violent high-energy heavy-ion collisions

Angular and energy distributions of fragments emitted from fast nucleus-nucleus collisions (Ne--> U at 250, 400, and 800 MeV/N) are calculated with use of nuclear fluid dynamics. A characteristic dependence of the energy spectra and angular distributions on the impact parameter is predicted. The preferential sideward emission of reaction fragments observed in the calculation for nearly central collisions seems to be supported by recent experimental data

Variable masses in fission and heavy-ion collisions

With the use of the cranking formula, the coordinate-dependent mass parameters of the kinetic-energy operator in fission processes and heavy-ion collisions are calculated in the two-center oscillator model. It is shown that the reduced mass and also the classical moment of inertia are obtained for large separations of the fragments. For small separations, however, the mass parameter for the motion of the centers of mass of the fragments is larger than the reduced mass by an order of magnitude

Nuclear equation of state from the nonlinear relativistic mean field theory

The properties of symmetric nuclear matter are investigated in the nonlinear relativistic mean field theory of nuclear matter. We consider the constraints imposed by four nuclear ground state properties on the coupling constants and on the equation of state at zero and at finite temperature. We find that the compression constant K(ρ0) as well as the temperature is irrelevant for the stiffness of the equation of state for m*(ρ0)≤0.7. The main point is that the relativistic mean field theory exhibits acausal and unphysical behavior for compressibilities below K(ρ0)=200 MeV. Every set of coupling constants with a negative quartic coupling constant c is unstable against small quantum fluctuations

Two different modes associated with the composite nucleus : the charge and mass distributions for exotic nuclear synthesis

The mass-dependent structure of the composite nucleus is shown based on three-dimensional timedependent Hartree-Fock calculations with Skyrme interactions (SLy4d and SkM*). One remarkable result is that the isovector monopole excitation dominantly appears for collisions of heavy nuclei, and the isovector dipole excitation for those of light ones. Such a difference found in the dynamical structure of composite nucleus plays a role in the equilibration of charge

Influence of shape fluctuations in relativistic heavy ion collisions

The influence of fluctuations of the shape degree of freedom in collisions of deformed nuclei with energies between 0.8 and 2.1 GeV/nucleon is analyzed on the basis of an intranuclear cascade simulation for the strongly deformed systems 46Ti+ 46Ti and 166Er+ 166Er. While there is a considerable sensitivity of the global event variables to the orientation for polarized beams and targets, this dependence disappears in the average over all orientations for impact parameter selected and integrated events. The dependence of the nuclear stopping and thermalization on the size of the system under consideration and on the bombarding energy is also investigated

Different deformations of proton and neutron distributions in nuclei

Different collective deformation coordinates for neutrons and protons are introduced to allow for both stretching and γ transitions consistent with experiments. The rotational actinide nuclei 234-238U and 232Th are successfully analyzed in this model. NUCLEAR STRUCTURE 232Th, 234-238U calculated B (E2) values, collective model

Suppression of Charge Equilibration leading to the Synthesis of Exotic Nuclei

Charge equilibration between two colliding nuclei can take place in the early stage of heavy-ion collisions. A basic mechanism of charge equilibration is presented in terms of the extension of single-particle motion from one nucleus to the other, from which the upper energy-limit of the bombarding energy is introduced for significant charge equilibration at the early stage of the collision. The formula for this limit is presented, and is compared to various experimental data. It is examined also by comparison to three-dimensional time-dependent density functional calculations. The suppression of charge equilibration, which appears in collisions at the energies beyond the upper energy-limit, gives rise to remarkable effects on the synthesis of exotic nuclei with extreme proton-neutron asymmetry.Comment: 4 pages, 4 figure