Calculation of triaxial superdeformation in ^(174)Hf

A two-dimensional Total Routhian Surface (TRS) calculation with the fixed hexa- decapole deformation ε4 = 0.03 was carried out for several configurations of 174Hf. Results indicate that the shell corrections have an important contribution to the formation of triaxial superdeformation in 174Hf and some possible configuration assignments are made to the 4 TSD bands experimentally found in 174Hf.

A systematic study of the superdeformation of Pb isotopes with relativistic mean field theory

The microscopically constrained relativistic mean field theory is used to investigate the superdeformation for Pb isotopes. The calculations have been performed with the four different interactions NL3, PK1, TM1 and NLSH, and show that there exists a clear superdeformed minimum in the potential energy surfaces. The excitation energy, deformation and depth of the well in the superdef.ormed minimum are comparable for the four different interactions. Furthermore the trend for the change of the superdeformed excitation energy with neutron number is correctly reproduced. The calculated two-neutron separation energy in the ground state and superdeformed minimum together with their differences are in agreement with the available data. The larger energy difference appearing in the superdeformed minimum reflects a lower average level density at superdeformations for Pb isotopes.

Possible existence of triaxial superdeformation in ～(172,174,176)W

Two-dimensional total routhian surface （TRS） calculations are carried out to determine the triaxial superdeformation （TSD） of the even-even nucleus 174W, and the result indicates that TSD state exists with deformation parameters ε2=0.42 andγ=34.7°. In the same way, the total routhian surfaces for the nuclei ^172,176W are also calculated. It shows that the neutron shell correction energy plays a key role in the formation of TSD nuclei ^172,174,176W, while the high j intruder orbitals and rotational energy are also crucial in the formation mechanism.

Quadrupole Pairing Correlations and Moments of Inertia of Superdeformed Nuclei

The Harmonic OseiUator Quadruple Pairing Cranking Hartree-Fock-Bogoliubov（HFB）theoreti-cal model is established and applied to the superdeforrned（SD）rotational states.The reduction and col-lapse of the pairing fields,including Y20,Y21 and Y22 fields at superdeformation and high spins,are stud-ied.It is found that the correct rotational frequency ω-dependence of the pairing fields is crucial for thetheory to reproduce the rising behavior of dynamic moment of inertia J（2） observed in the A=190 region,and the Y21 pairing contributes significantly to reducing the rising rate of J（2） and thus may strongly influ-enee the collective properties of SD nuclei.The calculated J（2） of 192H8 is in good agreement with the ex-perimental data up to （?）ω=0.32 MeV.

Description of the Superdeformed Bands of the Odd-Odd Nuclei in A ～ 150 Region

With the supersymmetry scheme including many-body interactions, the global property and the △I ＝ 4bifurcation in the superdeformed (SD) bands of odd-odd nuclei in A ～ 150 mass region are investigated systematically.Good results for the γ-ray energies, the dynamical moments of inertia, and energy differences △ Eγ - △ Erefγ are obtained.It shows that this approach is quite powerful in describing not only the SD bands in even-even and odd-A nuclei butalso those in odd-odd nuclei in the mass region.

Microscopic Mechanism of the ω Variation in Moments of Inertia for the Yrast Superdeformed Bands 194Tl(1a, 1b)

The variation in moments of inertia (J(1) and J(2)) with rotational frequency for the superdeformed bandsin odd-odd nuclei, 194Tl(la,lb), is investigated by using the particle-number conserving method for treating the pairinginteraction (monopole and quadrupole). The observed variations of J(1) and J(2) with ω are reproduced quite well inthe calculation and the contributions from each major shell are clearly displayed.

Study on Superdeformed Bands of ^(152)Dy and Its Neighboring Nuclei

152^Dy is the first observed superdeformed nucleus, whose band structure reflects the typical distribution of high j low Ω orbitals of superdeformed nuclei in A-150 mass region. The particle-number conserving treatment of the cranked shell model with monopole and quadrupole paring interactions is adopted to investigate the observed six superdeformed bands in 152^Dy. The π[523]7/2 orbital is emphasized for the first time to interpret the microscopic structure of band 2 and 3 of 152^Dy. A new comprehension is proposed on the basis of ever existing experimental and theoretical results, and the reliability is illustrated by several superdeformed bands of neighboring nuclei.

Configuration Assignment of Superdeformed Bands in Odd-A Hg nuclei

-By using particle-rotor model,the configuration of the superderformed(SD)bands in odd-A Hg nuclei is analysed.It is shown that the electromagnetic transitionproperties of the SD bands can be used to further identify the configuration.

Level Spin Assignment Of Superdeformed Bands for A～190 Region

Using the expression of level energies of rotational bands and least-squares fitto cascade gamma transition energies of superdeformed bands,level spins of 27superdeformed bands for 13 nuclei in.4～190 region are assigned and compared withthose of others.

Analysis of Identical.Superdeformed Bands

Identical superdeformed bands in 191Au and 191Hg have been investigated byusing particle-rotor model within the framework of the BCS （Bardeen-Cooper-Schrieffer） pairing correlation.The identity in the γ-transition energies in these bandsshows that the properties of specific individual orbitals may be important to understandidentical bands.

Calculations of Superdeformed Bands in j_(15/2^-)Model

Using the particle-rotor model,some features of superdeformed bands builtupon j15 orbitals have been investigated.An excellent agreement between the caleu-lated and observed transition energies,kinematic and dynamic moments of inertiaof Hg（bl）is obtained.

Analysis of Superdeformed Band of ^(193)TI

Superdeformed bands of 193TI are analyzed by using particle-rotor model inconnection with experimental data,considering the possible occurrence of triaxialshape.It is investigated that γ-transition energies and dynamic moments of inertia de-pend on γ-deformation and energy gap.

Further research on high-spin structure in ^(161)Lu

The two-dimensional total routhian surface (TRS) calculations were performed to probe into the triaxial superdeformed characteristics of a strongly populated band X2 in 161Lu. This band was identified as a triaxial superdeformed band by using our TRS method. We also got its formation mechanics,i.e. the neutron-shell correction energy plays a crucial role,while the rotating energy and the deformation-driving effect of high j intruder orbit i13/2 also play an additional role.

SU(5) symmetry of spdfg interacting boson model

The extended interacting boson model with s-, p-, d-, f- and g-bosons included (spdfg IBM)is investigated. The algebraic structure including the generators, the Casimir operators of the groups at the SU(5) dynamical symmetry and the branching rules of the irreducible representation reductions along the group chain are obtained. The typical energy spectrum of the symmetry is given.

Study of △I=2 staggering by perturbed particle-rotor model

AI=2 staggering in superdefonned nuclei has been investigated by a perturbed particle-rotor model, of which all observed features are reproduced in the calculations. It is pointed out that the C4symmetry in Hamiltonian is not the only cause of AI=2 staggering. This model can be used to make a fit to the experimental data in odd-A superdeformed nuclei.

Systematic odd-even differences in the moments of inertia of superdeformed bands and blocking effect

A comprehensive analysis of the superdeformed bands observed near A≈190 indicates that there exist systematic odd-even differences in the moments of inertia similar to that observed in normally deformed nuclei, which can be considered as compelling evidence for pairing and blocking effect in super-deformed nudei. With increasing rotational frequency the odd-even differences become weaker and weaker due to the Coriolis anti-pairing effects. Particularly, the odd-even differences in the dynamic moments of inertia become obscure when hω≥2 MeV, and in certain cases there emerges nearly identical value of J(2) for some neighboring nudei. However, the odd-even differences in the kinematic moments of inertia still remain to certain extent at the highest frequencies.

Band structure of superdeformed bands in odd-A Hg nuclei

Through particle-rotor model, band structure of superdeformed bands in odd-A Hg nuclei is analysed. An overall and excellent agreement between the calculated and observed kinematic and dynamic moments of inertia is obtained. The electromagnetic transition properties of SD bands can be used to identify the configuration with certainty.

Backbendings of superdeformed bands in ^(36,40)Ar

Experimentally observed superdeformed(SD) rotational bands in36Ar and40Ar are studied by the cranked shell model(CSM) with the pairing correlations treated by a particle-number-conserving(PNC) method.This is the first time that PNC-CSM calculations have been performed on the light nuclear mass region around A=40.The experimental kinematic moments of inertia J~((1))versus rotational frequency are reproduced well. The backbending of the SD band at frequency around ω =1.5 Me V in36Ar is attributed to the sharp rise of the simultaneous alignments of the neutron and proton 1 d5/2[202]5/2 pairs and 1 f7/2[321]3/2 pairs, which is a consequence of the band crossing between the 1 d5/2[202]5/2 and 1 f7/2[321]3/2 configuration states. The gentle upbending at low frequency of the SD band in40Ar is mainly affected by the alignments of the neutron 1 f7/2[321]3/2 pairs and proton 1 d5/2[202]5/2 pairs.The PNC-CSM calculations show that besides the diagonal parts, the off-diagonal parts of the alignments play an important role in the rotational behavior of the SD bands.

Band head spin assignment of superdeformed bands in 86Zr

Two parameter expressions for rotational spectra viz. variable moment of inertia （VMI）, ab formula and three parameter Harris w2 expansion are used to assign the band head spins （I0） of four rotational superdeformed bands in 86Zr. The least-squares fitting method is employed to obtain the band head spins of these four bands in the A - 80 mass region. Model parameters are extracted by fitting of intraband y-ray energies, so as to obtain a minimum root-mean-square （rms） deviation between the calculated and the observed transition energies. The calculated transition energies are found to depend sensitively on the assigned spins. Whenever an accurate band head spin is assigned, the calculated transition energies axe in agreement with the experimental transition energies. The dynamic moment of inertia is also extracted and its variation with rotational frequency is investigated. Since a better agreement of band head spin with experimental results is found using the VMI model, it is a more powerful tool than the ab formula and Harris w2 expansion.

Systematic study of rotational energy formulae for superdeformed bands in La and Ce isotopes

The experimental rotational spectra of superdeformed（SD） bands of 130La, 131Ce（1,2）, 132Ce（1,2,3） and133 Ce（1,2,3） in the A～130 mass region are systematically analyzed with the four parameter formula, power index formula, nuclear softness formula, and VMI model. It is observed that out of all the formulae, the four parameter formula suits best for the study of the 130La, 131Ce（1,2）, 132Ce（2,3） and 133Ce（1,2,3） SD bands. The four parameter formula works efficiently in determining the band head spin of the 130La, 131Ce（1,2） 132Ce（2,3） and 133Ce（1,2,3） SD bands. Good agreement is seen between the calculated and observed transition energies whenever the accurate spin is assigned. In 132Ce（1）, the power index formula is found to work better than the other three formulae. The dynamic moment of inertia is also calculated for all the formulae and its variation with the rotational frequency is investigated.