Evidence for a Possible E（5） Symmetry in ^130Xe

By analysing the energy spectrum and E2 transition branching ratios,we show that the E(5) symmetry predictions agree well with the experimental data of nucleus 130Xe,Compared the calculated results with those within the framework of the interacting boson model.It is found that the nucleus 130Xe is definitely a nucleus in the transitional region from U(5) to O(6) symmetry,130Xe is then another empirical evidence of the nucleus with E(5) symmetry.     

Inequalities of the electron density at the nucleus and radial expectation values of the ground state for the lithium isoelectronic sequence

The electron density at the nucleus, ρ(0), and the radial expectation values, (-2≤n≤10), of the ground state for the lithium isoelectronic sequence are calculated with a full core plus correlation (FCPC) wavefunctions. By using these obtained expectation values, the accurate inequalities of the electron density at the nucleus and the radial expectation values derived by Gálvez and Porras for these systems are examined and verified. The final results show that FCPC wavefunctions used in this work can give satisfactory results in full configuration space.     

Possible 1d5／2 and 2s1／2 Level Inversion in the Proton—Rich Nucleus ^23Al

The discovered proton halo nucleus of ^23Al is investigated in the nonlinear relativistic mean-field(RMF) model with deformation using the NL075 force parameter,It is shown that there is an energy inversion between the (5/2)^ (202)and (1/2)^ (211)orbitals in the ^23Al nucleus,which may produce a large enhancement of the reaction cross section compared with the neighbouring nuclei.Meanwhile,the NL075 force parameter may be better than the other RMF parameters for the calculation of the large defromed nucleus ^23Al.     

Description of 114 Cd in the E（5） Symmetry

By analysing the known low-lying levels and the E2 transition rates, it is shown that the empirical scheme of 114Cd is in good overall agreement with the predictions of the transitional dynamical symmetry E(5) proposed by Iachello [Phys. Rev. Lett. 85 (2000) 3580]. This suggests that 114Cd may be better described by an E(5) nucleus than a U(5) nucleus as known before.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of α-decay is extended to the regions around doubly magic spherical nucleus 208pb and around deformed shell closure 270Hs, respectively. The effects of spherical shell closures (N = 126 and Z = 82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical α-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus 208 Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of a-decays from the ground state of a parent nucleus to the ground state (0 ) of its deformed daughter nucleus and to the first excited state (2 ) are .calculated in the framework of the cluster model. The results indicate that a measurement of c spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus 270 Hs.     

Two-dimensional Langevin modeling of fission dynamics of the excited compound nuclei ~(188)Pt,~(227)Pa and ~(251)Es

A stochastic approach based on one-and two-dimensional Langevin equations is applied to calculate the pre-scission neutron multiplicity,fission probability,anisotropy of fission fragment angular distribution,fission cross section and the evaporation cross section for the compound nuclei ~(188)Pt,~(227)Pa and ~(251)Es in an intermediate range of excitation energies.The chaos weighted wall and window friction formula are used in the Langevin equations.The elongation parameter,c,is used as the first dimension and projection of the total spin of the compound nucleus onto the symmetry axis,K,considered as the second dimension in Langevin dynamical calculations.A constant dissipation coefficient of K,γk=0.077(MeV zs)~(-1/2),is used in two-dimensional calculations to reproduce the above mentioned experimental data.Comparison of the theoretical results of the pre-scission neutron multiplicity,fission probability,fission cross section and the evaporation cross section with the experimental data shows that the results of two-dimensional calculations are in better agreement with the experimental data.Furthermore,it is shown that the two-dimensional Langevin equations together with a dissipation coefficient of K,γk=0.077(MeV zs)~(-1/2),can satisfactorily reproduce the anisotropy of fission fragment angular distribution for the heavy compound nucleus(251)~Es.However,a larger value of γk=0.250(MeV zs)~(-1/2)is needed to reproduce the anisotropy of fission fragment angular distribution for the lighter compound nucleus(227)Pa.     

Isotopic Trends of Fusion Probability in Reactions with Zn Isotopes Bombarding ^208Pb

where σc is the effective capture cross section for the transition of the colliding nuclei over the entrance Coulomob arrier, Wsur is the survival probability of the compound nucleus. In the DNS model, the compound nucleus is reached by a series of transfers of nuclcons from the light nucleus to the heavy one. Thc dynamics of the DNS is considered as a diffusion process in the mass asymmetry degree of freedom η=(A1 - A2)/(A1 A2) (A1 and A2 are the mass numbers of the DNS nuclei), PCN is the complete fusion probability, here it is calculated by solving the Master equation numcrically[2]. The fusion barrier Bfus in η supplies a hindrance for fusion.     

Generalization of α-Decay Cluster-Model to Nuclei Near Spherical and Deformed Shell Closures

The cluster model of a-decay is extended to the regions around doubly magic spherical nucleus ^208Pb and around deformed shell closure ^270Hs, respectively. The effects of spherical shell closures (N=126 and Z=82) on α-decay are investigated by introducing an N-dependent α-preformation factor and a Z-dependent one inspired by a microscopic model. Good agreement between the theoretical a-decay half-lives and the measured ones is obtained for the spherical nuclei near the doubly magic nucleus ^208Pb, where the nuclear shell effect is included in the expression of α-preformation factor. The cluster model is also generalized for the decay of deformed nuclei. The branching ratios of α-decays from the ground state of a parent nucleus to the ground state (0^ ) of its deformed daughter nucleus and to the first excited state (2^ ) are calculated in the framework of the cluster model. The results indicate that a measurement of α spectroscopy is a feasible method to extract the information of nuclear deformation of superheavy nuclei around the deformed nucleus ^270Hs.     

Isospin and symmetry structure in 34S

The interacting boson model-3(IBM-3) has been used to study the energy levels and electromagnetic transitions for the nucleus 34 S.The main components of the wave function,isoscalar and isovector parts in the M1 and E2 transitions for low-lying states have been investigated.According to this study,the theoretical calculations are in agreement with experimental data,and the nucleus 34 S is in transition from U(5) to S U(3).     

Identical Bands and Alignment in ^193,194Tl

The microscopic mechanism of the identical bands in odd-odd nucleus ^194Tl and its neighbour odd-A nucleus ^193Tl are investigated using the particle-number conserving method with monopole and quadrupole pairing interaction. It is found that the blocking effect plays an important role in the variation of moments of inertia (J^(1) and J^(2)) with rotational frequency for the superdeformed bands and identical bands. The alignment of 194T1 bands with respect to the ^193Tl(1) band used as a reference is also discussed.     

Angular Anisotropy of the Fission Fragments in the Dinuclear System Mo del

A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system (DNS) model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the angular distribution of fission fragments for the neutron–induced fission of 239Pu.     

Static versus energy-dependent nucleus–nucleus potential for description of sub-barrier fusion dynamics of _8~(16)O+_(50)~(112,116,120)Sn reactions

The static and energy-dependent nucleus–nucleus potentials are simultaneously used along with the Wong formula for exploration of fusion dynamics of168O+112,116,12050 Sn reactions. The role of internal structure degrees of freedom of colliding pairs, such as inelastic surface vibrations, are examined within the context of coupled channel calculations performed using the code CCFULL. Theoretical calculations based on the static Woods–Saxon potential along with the one-dimensional Wong formula fail to address the fusion data of168O+112,116,12050 Sn reactions.Such discrepancies can be removed if one uses couplings to internal structure degrees of freedom of colliding nuclei.However, the energy-dependent Woods–Saxon potential model(EDWSP model) accurately describes the sub-barrier fusion enhancement of168O+112,116,12050 Sn reactions. Therefore, in sub-barrier fusion dynamics, energy dependence in the nucleus–nucleus potential governs barrier modification effects in a closely similar way to that of the coupled channel approach.     

Systematical law of (n, γ) reaction cross sections of even-even nuclei

We have derived a formula for the neutron radiative capture cross section in the framework of a statistical model approach to nuclear reactions. Based on this formula, new systematics are established between the (n, γ) reaction cross section and the energy level density of a compound nucleus or a relative neutron excess of an even-even target nucleus for neutron incident energy above the resonance region to MeV. Good agreement with experimental data suggests that this new systematical law is helpful to analyze the experimental data.     

Empirical Example of Nucleus with Transitional Dynamical Symmetry X（5）

By analysing the energy spectrum,E2 transition rates and branching ratios,it is shown explicitly that the nucleus ^150Nd provides an empirical example with X(5) symmetry at the critical point of the transition from U(5) to SU(3) symmetry.     

Description of the critical point symmetry in ~(124)Te by IBM-2

Based on the neutron and proton degrees of freedom, low-lying energy levels, E2, M1, and E0 transition strengths of nucleus ~(124)Te have been calculated by the neutron-proton interacting boson model. The calculated results are reasonably consistent with the experimental data. By comparing the key observables of the states at the critical point of U_(πv)(5)-O_(πv)(6) transition with the experimental data and calculated results, we show that the ~(124)Te is a possible nucleus at the critical point of the second-order phase transition from vibration to unstable rotation, and such a critical point exhibits slight triaxial rotation. The 0_2~+ state of ~(124)Te can be interpreted as the lowest state of the first-excited family of the intrinsic levels in the critical point symmetry.     

~(13)C(α, n)~(16)O background in a liquid scintillator based neutrino experiment

α from natural radioactivity may interact with a nucleus and emit a neutron. The reaction introduces the background to the liquid scintillator(LS) based neutrino experiments. In the LS detector, α comes from 238 U,232Th,and 210 Po decay chains. For Gadolinium-doped LS(Gd-LS) detector, α also comes from 227 Ac. The nucleus 13 C is a natural component of Carbon which is rich in the LS. The background rate and spectrum should be subtracted carefully from the neutrino candidates. This paper describes the calculation of neutron yield and spectrum with uncertainty estimated. The results are relevant for many existing neutrino experiments and future LS or Gd-LS based experiments.     

Doublet bands at borders of A ≈ 130 island of chiral candidates: Case study of ~(120)I

Positive-parity doublet bands were reported in ~(120)I. Based on these, we discuss the corresponding experimental characteristics, including rotational alignment, and re-examine the corresponding configuration assignment.The self-consistent tilted axis cranking relativistic mean-field calculations indicate that the doublet bands are built on the configuration πh_(11/2)■νh_(11/2)~(-1). By adopting the two quasiparticles coupled with a triaxial rotor model, the excitation energies, energy staggering parameter S(I), B(M1)/B(E2), effective angles, and K plots are discussed and compared with available data. The obtained results support the interpretation of chiral doublet bands for the positive-parity doublet bands in ~(120)I, and hence identify this nucleus as the border of the A ≈ 130 island of chiral candidates.     

Shape evolution of ~(72,74)Kr with temperature in covariant density functional theory

The rich phenomena of deformations in neutron-deficient krypton isotopes,such as shape evolution with neutron number and shape coexistence,have attracted the interest of nuclear physicists for decades.It is interesting to study such shape phenomena using a novel way,e.g.by thermally exciting the nucleus.In this work,we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach,and apply this approach for the study of shape evolution in ~(72,74)Kr with increasing temperature.For ~(72)Kr,with temperature increasing,the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T~0.9 Me V,and then changes from oblate to spherical at T~2.1 Me V.For ~(74)Kr,its global minimum is at quadrupole deformation β_2~-0.14 and abruptly changes to spherical at T~1.7 MeV.The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc =0.6?p(0),where ?p(0) is the proton pairing gap at zero temperature.The signatures of the above pairing transition and shape changes can be found in the specific heat curve.The single-particle level evolutions with temperature are presented.     

Rotational to vibrational evolution in some rotational-like nuclei

The excitation spectra of nuclei in the regions 150156Gd. Also we have shown the result of the nucleus ¹⁰²Ru which is given as an example of the reverse transition, i.e., vibration to rotation. The TRS plots reveal that, as the spin increases up the band, the former nucleus becomes slightly soft in γ and β direction, whereas the latter becomes rigid in γ direction.     

Production of super-heavy nuclei in cold fusion reactions

A model for cold-fusion reactions related to the synthesis of super-heavy nuclei in collisions of heavy projectile-nuclei with a ²⁰⁸Pb target nucleus is discussed.In the framework of this model,the production of the com-pound nucleus by two paths,the di-nuclear system path and the fusion path,are taken into account simultaneously.The formation of the compound nucleus in the framework of the di-nuclear system is related to the transfer of nucle-ons from the light nucleus to the heavy one.The fusion path is linked to the sequential evolution of the nuclear shape from the system of contacting nuclei to the compound nucleus.It is shown that the compound nucleus is mainly formed by the fusion path in cold-fusion reactions.The landscape of the potential energy related to the fusion path is discussed in detail.This landscape for very heavy nucleus-nucleus systems has an intermediate state,which is linked to the formation of both the compound nucleus and the quasi-fission fragments.The decay of the intermediate state is taken into account in the calculation of the compound nucleus production cross sections and the quasi-fission cross sections.The values of the cold-fusion cross sections obtained in the model agree well with the experimental data.