Mitsuo Sano

Phase Transition and Level Density of Atomic Nuclei

The effect of the paIrIng mieractlOn on nuclear spectlum IS btudied WIth the aid of the modern theory of superconductivIty developed by B C Sand BogollUbov As the states near the ground sLate have been !:>tuchecl by many authorb, we employ d btailbtlcal dyxad namIcal apploach to examllle the grobs behavIOur of the excIted btates For the nucleI of medlUm weIght, a phase trdnbltlOn Ib prechcted at the twnsltlOn energy of some 5 to 10 Mev The level denSIty below thib energy IS greatly dIfferent from that expected on extraxad polatlllg It from hIgher enel gy blde It Ib dIbcubsed that the Imaglllary part of the optical potentIal can be much smaller than that obtallled by the Fel mi gas model

Generalized Hartree-Fock method and rotational states

Abstract The generalized Hartree-Fock method is applied to a description of rotating nuclei. This method gives a self-consistent description of the rotational motion based on the cranking model and effects of rotation on the pair correlation. The Coriolis force prevents the formation of coupled pairs. Thus there is an upper bound of the angular momentum such that a nucleus can be superconducting. The reduction of the energy gap results in an increase in the moment of inertia. The stability of rotational states is also discussed. The emphasis here is that, even if low-lying excited states with small angular momenta are stable, for sufficiently large angular momentum the Coriolis force leads to the instability of rotational states.

Kaon production in the nuclear fireball model

Abstract Inclusive K + spectra in collisions of 2.1 GeV/nucleon Ne + NaF are calculated on the basis of the nuclear fireball model. The calculated result is compared with the one obtained from the linear cascade model by Randrup and Ko.

Semiclassical analysis of the spin polarization of 12B in the 100Mo(14N, 12B)102Ru reaction

Abstract Polarization of 12 B in the 100 Mo( 14 N, 12 B) 102 Ru reaction at 90 MeV incident energy is studied on the basis of the semiclassical theory of transfer reactions proposed by Brink. Gross behaviors of both the polarization and the cross section as functions of product kinetic energy can be predicted successfully by the theory. But disagreement in the numerical values of the polarization is found for low-energy 12 B.

TWO-NEUTRON TRANSFER REACTIONS ON NUCLEI IN THE TRANSITIONAL REGION.

Abstract The possibility of coexistence of spherical and deformed states in samarium isotopes is explored by analyzing the experimental data of the two-neutron transfer reactions, and the moment of mixing of the coexisting states and their deformation parameters are determined.

Formation and Disintegration of High-Density Nuclear Matter in Heavy-Ion Collisions Nonrelativistic Approximation

The formation of high-density nuclear matter which may be expected to be attained in high-energy heavy-ion collisions and the subsequent disintegration of dense matter are investixad gated by means of the hydrodynamics. Head-on collisions of identical nuclei are considered in the nonrelativistic approximation. The compressed density cannot exceed 4 times of the normal one so long as the freedom of only nucleons is considered, and can become higher than 4 times when other freedoms such as the productions of mesons and also nucleon isobars are additionally taken into account. The angular distributions for ejected particles predominate both forwards and backwards at low collision energies, corresponding to the formation of nuclear density less than 2 times of the normal density and become isotropic at the point of 2 times of the normal one. As the collision energy increases further, lateral ejection is intensified gradually.

Stability of nuclear rotational states

Abstract The stability of rotational states described by using a procedure of the Hartree-Fock-Bogoliubov method is discussed. The stability condition is obtained in a general form and some of its properties are examined with the aid of simplifying approximations. It is pointed out in conclusion that the Coriolis force might lead to the instability of rotational states for sufficiently large angular momenta. The instability of rotational states is caused by the instability of the pairing density, and also by that of the nuclear density distribution. In the former case it is shown that below the critical angular momentum, a first-order phase transition takes place and in some cases the rotational band breaks off. In the latter case, it might be considered that the assumption of an axially symmetric deformation is broken or large change of the equilibrium deformation is brought suddenly. Then discontinuous change of the rotational level might be seen at the unstable point.

Effective E3 transition moments for 1h112 single proton states in N ≈ 82 nuclei

Electric octupole (E3) matrix elements for the single-quasiparticle transitions 1h112 → 2d52 were calculated in the framework of an E3 phonon-particle coupling model. Pairing, quadrupole and octupole interactions are taken into account. The quadrupole interaction strengths were obtained so as to reproduce the E2 phonon energies in neighboring doubly even nuclei. The experimental values of geff(E3)/g(E3) ≈ 3 for the effective E3 coupling constants (charge) were well reproduced by using a simple A-dependent octupole interaction strength, which also reproduces as well the E3 phonon energies in neighboring doubly even nuclei.

Two-Neutron Transfer Reactions on Nuclei around N=82 Closed Shell

The superfluid model was used to calculate the ground-state to ground state reactions on Zr and Nd isotopes. The calculated and experimental cross sections for (p,t) reactions leading to the ground states of the Nd isotopes are shown explicitly; agreement of varying quality is obtained for different cases. In order to reproduce the experimental values for the Zr and Nd isotopes, the energy interval between the levels above and below the closed shell must be taken smaller than that obtained from the separation enengies. The data indicate the necessity of taking into account the change in the nuclear deformations of the target and residual nuclei. Calculated angular distributions are in good agreement with experimental data. The success in reproducing the experimental cross sections for two-neutron transfer reactions suggests that the Nd isotopes, except for /sup 142/Nd, are in the superfluid phase. These superfluid properties may arise from couplings between the valence protons and neutrons. (2 figures, 1 tables) (RWR)

CENTRIFUGAL STRETCHING EFFECT TO INTRA-BAND E2-TRANSITION RATES.

Abstract The angular momentum projection method is applied to the calculation of the intra-band B(E2)-transition rates of even nuclei in the rare-earth region. It is shown that the centrifugal stretching model can reproduce the experimental results for the transitions in the higher spin states of the ground state rotational band with satisfying accuracy.