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.     

Nuclear properties of Z=114 isotopes and shell structure of ~(298)114

The two-neutron separation energies(S_(2n)) and α-decay energies(Q_α) of the Z=114 isotopes are calculated by the deformed Skyrme-Hartree-Fock-Bogoliubov(SHFB) approach with the SLy5,T22,T32 and T43 interactions.It is found that the tensor force effect on the bulk properties is weak and the shell closure at N=184 is seen evidently with these interactions by analyzing the S_(2n) and Q_α evolutions with neutron number N.Meanwhile,the single-particle energy spectra of ~(298)114 are studied using the spherical SHFB approach with these interactions to furthermore examine the shell structure of the magic nucleus ~(298)114.It is shown that the shell structure is almost not changed by the inclusion of the tensor force in the Skyrme interactions.Finally,by examining the energy splitting of the three pairs of pseudospin partners for the protons and neutrons of ~(298)114,it is concluded that the pseudospin symmetry of the neutron states is preserved better than that of the proton states and not all of the pseudospin symmetries of the proton and neutron states are influenced by the tensor force.     

Properties of the Alpha Decay Chain Nuclei of ^310 126, ^292 120 and ^298 114

The properties of the a decay nuclei of^310 126, ^292 120 and ^298 114 are investigated in the deformed relativistic meanfield model. The nuclear properties are investigated with the TMA and NL-Z2 parameter sets, and compared with Moller‘s result [At. Data Nucl. Data Tables 59 (1995) 185]. The results show that the a decay energy increases systematically with the increasing proton number. Meanwhile, the a decay energy has a minimum value at the point of shell closure. It is also found that among the three nuclei, ^292 120 is more possible to be the next doubly magic nucleus.     

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.     

Oscillation of Hot Fissioning Nuclei around a Saddle Point

Three time scales of a fissioning nucleus starting from the ground state to the scission point are defined and calculated by the Monte Carlo method. The result shows that the time of oscillating around the saddle point is longer than both the mean first passage time from the ground state to the saddle point and the time of descent from the saddle to scission points. Thus it is suggested that more neutrons could be emitted from a hot heavy fissioning nucleus during the period of the stretching and contracting of the deformation process.     

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.     

Influence of Nuclear Deformation on the Potential Energy Surface in Di—Nuclear Model

Influence of the nuclear deformation on the potential energy surface(PES) in a di-nuclear system is studied in details.It is found that the PES shape changes greatly due to the deformation effect.The top point of the PES could be reduced significantly,which implies that the optimum excitation energy could also be reduced greatly and may enhance the fromation probability of the compound nucleus.The dynamical deformaiton as a function of the reaction time in the reaction process is dramatic.The Z/N ratios of fragments tend to follow that of the compound nucleus during the nucleon exchange process,but to fluctuate.     

Structure of the πg7／2[404]7／2^＋ Band in Odd Proton Nucleus ^123I

High spin states of the odd proton nucleus ^123I have been populated in the reaction ^116Cd(^14N, 5n2p) at a beamenergy of 65 MeV. Two previously known positive-parity △I = 2 sequences have been extended up to 31/2^ and41/2^ . In addition, a number of △I = 1 transitions linking the two △I = 2 sequences have been observed. It issuggested that both the △I = 2 sequences are built upon the oblate πg7/2[404]7/2^ Nilsson configuration.     

Possible Experimental Evidence of a Moderate Proton Halo in ^29S

The total reaction cross sections (TRCSs) of^29S ^28Si have been measured at intermediate energies. An obvious enhancement in TRCS of ^29S is observed as compared with its neighbouring nuclei. The TRCSs of ^29S ^28Si arecal culated with the modified Glauber theory in the optical limit and few-body approaches. The different factor d as a possible measure of halo appearance is deduced from the experimental and theoretical data. It is well accepted that ^27p is a proton halo nucleus. Although not as anomalous as ^27p, the different factor d of ^29S is obviously larger than that of its neighbouring isotones of N = 13. This result indicates that a moderate proton halo may exist in ~9S nucleus. We calculate the total reaction cross sections for ~9S with the modified Glaubertheory as a function of incident energy and compare the results with those for 2rSi which is a core nucleus 0f29S.The measured TRCSs of 27Si4-2SSi can be described to be satisfactory by the modified Glauber theory of theoptical limit approach. Although a diffused nuclear density distribution is used, the theories still inadequatelypredict the experimental TRCSs of 29S4-2SSi, which further indicates the possibility of proton halo in 29S.     

Fusion Barrier of Super-heavy Elements in a Generalized Liquid Drop Model

The macroscopic deformed potential energies for super-heavy elements Z = 110,112,114,116,118 arc determined within a generalized liquid drop model (GLDM). A quasi-molecular mechanism is introduced to describe the deformation of a nucleus in the GLDM and the shell model simultaneously. The macroscopic energy of a twocenter nuclear system in the GLDM includes the volume-, surface-, and Coulomb-energies, the proximity effect at each mass asymmetry, and accurate nuclear radius. The shell correction is calculated by the Strutinsky method and the microscopic single particle energies are derived from a shell model in an axially deformed Woods-Saxon potential with the quasi-molecular shape. The total potential energy of a nucleus can be calculated by the macro-microscopic method as the summation of the liquid-drop energy and the Strutinsky shell correction. The theory is applied to predict the fusion barriers of the cold reactions ^64Ni ^208 spb → ^272 110*, ^70Zn ^208pb → ^278 112*, ^76Ge ^208seb → ^284 114*,^82Se ^208pb → ^29 116*, ^86Kr ^208pb → ^294 118*. It is found that the neck in the quasi-molecular shape is responsible for the deep valley of the fusion barrier. In the cold fusion path, double-hump fusion barriers could be predicted by the shell corrections and complete fusion events may occur.     

Effects of Target Deformation on the Synthesis of Superheavy Nucleus 283^112

We investigate the effects of target deformation on the synthesis of superheavy nucleus 283^112 in the framework of the extra-push model. Our results show that the cross sections of the 3n evaporation residue in the 48^Ca 238^U reaction for the case of β2=0.275 are several times larger than those of β2=0. Meanwhile, the peak position of ER excitation function in the case of the deformed target is shifted to lower energy as compared to that of the spherical target.     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

Odd-Even Effects of the Survival Probability for Superheavy Compound Nuclei

The survival probability of the superheavy compound nuclei with Z=114 is studied with the statistical model. It is found that the survival probability shows drastic odd-even effects. The odd-A compound nuclei have higher survival probability by evaporating three neutrons as compared with their neigbouring even-A compound nuclei.     

Theoretical Investigation of the Exotic Structure of the Mirror Nuclei ^17Ne and ^17N

The exotic structures of the ground state of the mirror nuclei ^17Ne and ^17N are investigated by means of the asymptotic normalization coefficient （ANC） method to explore the role of the Coulomb interaction, The probebilities of a valence nucleon outside the binding-potential are P = 56.69±2.98/7.46% for ^17Ne and P = 45.51±2.32/5.81% for ^17N. The rms radii are （r^2）^1/2 = 5.06±0.11/0.30 fm and （r^2）^1/2=4.24±0.06/0.16 fm, respectively. The results obtained are nearly independent of the potential parameters. According to the halo occurrence conditions, it is suggested that ^17Ne is a two-proton halo and ^17N is a two-neutron skin. Moreover, two effects of the Coulomb interact-ion on the exotic structure are analysed. From the present results, the exotic structure of the nucleus in the proton-rich side is more obvious than that of its mirror nucleus because of the Coulomb interaction.     

Branching Ratios of α Decay for Nuclei near Deformed Shell Closures

The generalized liquid drop model （GLDM） is extended to the region around deformed shell closure ^270Hs by taking into account the excitation energy EI＋ of the residual daughter nucleus and the centrifugal potential energy Vcen（r）. 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 GLDM. The results support the proposal that a measurement of a spectroscopy is a feasible method to extract information on nuclear deformation of superheavy nuclei around the deformed nucleus ^270Hs.     

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.     

Roles of Isospin in Evaporation Residue Cross Section as a Probe of Nuclear Dissipation

The influence of isospin on the excess of evaporation residue cross section over its standard statistical-model value for nuclei ^194pb, ^200Pb, and ^206pb is studied via a Langevin equation coupled with a statistical decay model. The magnitude of this excess for a low-isospin fissioning nucleus is shown to be larger and its dependence on the nuclear viscosity coefficient to be stronger than those of a high-isospin fissioning nucleus. These results suggest that to obtain a more accurate information of viscosity coefficient inside the saddle point by measuring evaporation residue cross sections, we had better choose those compound systems with small isospin.     

High spin states in neutron-rich ~(106)Tc nucleus

The high spin states of the neutron-rich odd-odd 106Tc nucleus have been reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. A previously known collective band is confirmed and expanded, and a new collective band is newly identified. Several levels in previous report in 106Tc are reexamined and they belong to the members of a band in 107Tc. The total Routhian surface (TRS) calculations show that the 106Tc has triaxial shape. The spins and parities as well as the configurations f...     

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.     

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.