Search for chiral bands in A ～ 110 neutron-rich nuclei

High spin states in A ～ 110 neutron-rich 106Mo, 110Ru and 112Ru nuclei have been reinvestigated by measuring the prompt γ-rays from the spontaneous fission of 252Cf. Two similar sets of bands are observed to high spins in each of three nuclei. Through analyzing of characters of the band structures, the chiral doublet bands are suggested in 106Mo, 110Ru and 112Ru.     

Probing shell structure in neutron-rich nuclei with in-beam γ-spectroscopy

The structure of neutron-rich light nuclei around N = 20 and 28 has been investigated at GANIL by means of in-beam gamma-spectroscopy using fragmentation reactions of ³⁶S and ⁴⁸Ca beams on a Be target. Gamma-decay of relatively high-lying excited states have been measured for the first time in nuclei around ³²Mg and ⁴⁴S. Level schemes are proposed and discussed for a large number of these neutron-rich nuclei around N = 20 and N = 28. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: azaiez@ipno.in2p3.fr     

New multi-phonon gamma vibrational bands in A∼110 neutron-rich nuclei

The high spin states of neutron-rich ¹⁰³Nb, ¹⁰⁷Tc and ¹⁰⁹Tc nuclei in A～110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. In ¹⁰³Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In ¹⁰⁷Tc and ¹⁰⁹Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified. The two-phonon bands are first observed in odd-Z nuclei. The characteristics for these band structures have been discussed.     

New multi-phonon gamma vibrational bands in A～110 neutron-rich nuclei

The high spin states of neutron-rich 103Nb, 107Tc and 109Tc nuclei in A~110 region have been investigated by measuring prompt γ-γ-γ coincident measurements populated with the spontaneous fission of 252Cf with the Gammasphere detector array. In 103Nb, one-phonon K = 9/2 and two-phonon K = 13/2 γ-vibrational bands have been identified. In 107Tc and 109Tc, one-phonon K = 11/2 and two-phonon K = 15/2 γ-vibrational bands, in which the zero-phonon bands are based on K=7/2 excited states, have also been identified...     

Structure of neutron-rich nuclei around A ⋍ 100

Neutron-rich isotopes of Mo (Z=42) around A ⋍ 100 have been investigated within the formalisms of cranked Nilsson Strutinsky and CHFB, to study several interesting features of nuclear structure in this mass region. The total energy/routhian surfaces have been generated for the isotopes of Mo ranging from A ⋍ 96 − 112, as a function of deformation (β ₂ and γ) for ground state and higher angular momentum states. Results of calculations using two different formalisms have been compared and combined to have a better understanding of the underlying mechanism of shape evolution.     

K~π=5~- rotational bands in neutron-rich Mo,Ru,and Pd nuclei

The collective rotations of the K~π = 5~- configuration in neutron-rich Mo,Ru and Pd isotopes were systematically investigated by the configuration-constrained cranking shell model based on the Skyrme Hartree-Fock method with pairing treated by shell-model diagonalization.The calculations efficiently reproduce the experimental moments of inertia of both the ground-state and side bands.Rotational bands built on two-particle K~π = 5~- configurations have been the subject of intense study.Possible configurations were assigned to the observed 5~- bands in ~(102-106) Mo,~(108-112) Ru and ~(112-114) Pd.We predict the existence of the 5~-bands in ~(108,110) Mo.These results provide deep insights into the structure of neutron-rich nuclei,and provide useful information for future experiments.     

Decay spectroscopy of neutron-rich nuclei with A ≃ 100

We review structure data obtained by decay spectroscopy of neutron-rich nuclei of mass close to 100. Emphasis is put on the contribution of experiments at IGISOL in the nineties. They confirmed the earlier postulated shape coexistence in the fast shape-transition region between N = 58 (spherical ground states and low collectivity) and N = 60 (strong axial deformation). A detailed spectroscopic study of the A = 99 chain established the upper-Z limit of the N = 56 shell closure region with ⁹⁹Nb, owing to striking similarities with ⁹⁷Y. A consequence of the N = 56 closure is that the s _1/2 odd-neutron becomes the ground state of the most neutron-rich N = 57 isotones, starting with ⁹⁹Mo, instead of the degenerated d _5/2 and g _7/2 subshells familiar in the tin region. Consequences on the change of spin on astrophysical r-process calculations are briefly discussed. Finally, we say a few words about neutron-rich rhodium and palladium isotopes near the neutron midshell where regular and intruder states coexist very close to each other.     

Relativistic γ-scaling and the Coulomb sum rule in nuclei

In this paper dividing factors G_L and G_T are constructed for the longitudinal and transverse responses of the relativistic Fermi gas in such a way that the reduced responses so obtained scale. These factors parallel another dividing factor studied previously, H_L, that yields a (different) reduced response which fulfills the Coulomb sum rule. G_L, G_T and H_L are all found to be only very weakly model-dependent, thus providing essentially universal dividing factors. To explore the residual degree of dependence which remains, the scaling and sum rule properties of several specific models have been considered. It is seen that the relativistic Fermi gas (by construction) and also typical shell-model reduced responses successfully scale and satisfy the Coulomb sum rule, as do experimental results at medium to high momentum transfers. On the other hand, it is observed that the quantum hadrodynamic model does so only if interaction effects become weaker with increasing momentum transfer, as predicted in the most recent versions of that model.     

A study of morphological and compositional evolution of nanoprecipitates in the Zr–Nb system and their transformational behavior

The metastable transformational behavior (both martensitic and omega) along with compositional and morphological evolution of bcc β precipitates, dispersed in the hcp α matrix of a Zr–1 wt% Nb alloy, were studied as a function of temperature and time. The evolution of the chemical composition of the β phase suggested preference towards metastable compositions having Nb content higher than the equilibrium value. Thermodynamic analysis showed that the metastable chemical compositions are the driving force for the nucleation of such β precipitates. The β to martensite transformation was observed to be possible only if β precipitate size exceeded a critical value of 160?nm. Micromechanical modeling was performed to estimate the critical size of β precipitate required to induce martensite transformation and the model predictions were in close agreement with the experimental observations. The omega transformation, on the other hand, showed less size dependence.     

The conversion width of the σ- and ξ-hyperons in nuclei and the one-meson exchange

The conversion width in nuclear matter for and is estimated in the frame of one-mesonexchange model (OMEM). There is a considerable reduction of the width for if additional mesons besides are taken into account. The expected width for is about 3 MeV.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.     

Structural evolution of ZrO2–mullite nanocomposites from the Si–Al–Zr–O amorphous bulk

ZrO₂–mullite nanocomposites were fabricated by in-situ-controlled crystallization of Si–Al–Zr–O amorphous bulk at 800–1250°C. The structural evolution of the Si–Al–Zr–O amorphous, annealed at different temperatures, was studied by X-ray diffraction, infrared, Laser Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The materials consisted of an amorphous phase up to 920°C at which phase separation of Si-rich and Al, Zr-rich clusters occurred. The crystalline phases of t-ZrO₂ and mullite were observed at 950°C and 1000°C, respectively. Mullite with a tetragonal structure, formed by the reaction between Al–Si spinel and amorphous silica at low temperature, changed into an orthorhombic structure with the increase of temperature. It was the phase segregation that improved crystallization of the Si–Al–Zr–O amorphous bulk. The anisotropic growth of mullite was observed and the phase transformation from t-ZrO₂ to m-ZrO₂ occurred when the temperature was higher than 1100°C.     

Spherical and Deformed Shell Closures in Superheavy nuclei

The structure of superheavy nuclei has been studied using the macroscopic-microscopic model. The macroscopic energy was calculated with the continuous medium model in which the energy is expressed as a function of nucleon densities. The deformations and structures of superheavy nuclei were systematically investigated. Calculations reproduce well the available data of experimental α-decay energies and half-lives. The investigation of single-particle levels shows that the shell structure is deformation and isospin dependent. Potential-energy-surface calculations display that superheavy nuclei have in general harder shapes than the nuclei of other mass regions.     

Structure of two-loop evolution kernels and evolution of the pion wave function in ϕ(6)3 and QCD

The general structure of the two-loop nonforward evolution kernels is investigated in the ϕ₍₆₎³ model and QCD. The solution of the two-loop evolution equations is constructed in both models. In QCD, the contribution of the two-loop corrections to the wave function evolution is estimated numerically.     

Odd-even nuclei in the A ≈ 100 nuclear region

Extensive calculations for the odd-neutron Ru-Pd isotopes and odd-proton Tc-Rh isotopes for both positive- and negative-parity states within the proton-neutron interacting boson-fermion model are presented. The results on energy levels, electromagnetic properties and spectroscopic strengths of one nucleon transfer reactions are compared with experiments. A general good agreement is obtained.