摘要:

The orientation of the angular momentum vector with respect to the triaxial density distribution selects a left‐handed or right‐handed system principal axes. This breaking of chiral symmetry manifests itself as pairs of nearly identical &Dgr;I= 1‐bands. The chiral structures combine high‐j particles and high‐j holes with a triaxial rotor. Tilted axis cranking calculations predict the existence of such configurations in different mass regions. There is experimental evidence in odd‐odd nuclei around mass 134. The quantized motion of the angular momentum vector between the left‐ and right‐handed configurations, which causes the splitting between the chiral sister bands, can be classified as tunneling (chiral rotors) or oscillation (chiral vibrators). © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556636

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A particle plus triaxial rotor model was applied to odd‐odd nuclei in theA∼ 130 region in order to study the unique parity&pgr;h11/2⊗&ngr;h11/2rotational bands. With maximum triaxiality assumed and the intermediate axis chosen as the quantization axis for the model calculations, the two lowest energy eigenstates of a given spin have chiral properties. The independence of the quantityS(I)on spin can be used as a new criterion for chirality. In addition, a diminishing staggering amplitude ofS(I)with increasing spin implies triaxiality in neighboring odd‐Anuclei. Chiral quartet bases were constructed specifically to examine electromagnetic properties for chiral structures. A set of selection rules unique to chirality was derived. Doublet bands built on the&pgr;g9/2⊗&ngr;h11/2configuration have been discovered in odd‐odd104Rhusing the96Zr(11B, 3n)reaction. Based on the discussed criteria for chirality, it is concluded that the doublet bands observed in104Rhexhibit characteristic chiral properties suggesting a new region of chirality aroundA∼110. In addition, magnetic moment measurements have been performed to test the&pgr;h11/2⊗&ngr;h11/2configuration in128Csand the&pgr;g9/2⊗&ngr;h11/2configuration in104Rh. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556637

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Triaxiality in nuclei influences many spectroscopic quantities related to the rotational band structure in deformed nuclei. Signature effects are expected in energies as well as in electromagnetic properties. Yet such effects may also arise as a result of the interplay of mechanisms not related to triaxiality. In contrast, the wobbling mode is uniquely related to triaxiality and introduces a series of bands with increasing wobbling phonon number,nw. The pattern of &ggr;‐transitions between the wobbling excitations will be influenced by the presence of an aligned particle. Recently, evidence for the wobbling mode was obtained, and even a two‐phonon wobbling excitation has now been identified in163Lu. The similarity between the data in163Lu and newly established bands and connecting transitions in the neighbouring nuclei,165Lu and167Lu, indicates that wobbling may be a more general phenomenon in this region. The higher phonon wobbling description shows some anharmonicity, but the characteristic large &Dgr;nw= 1 E2 strength is observed. The wobbling interpretation is based on comparison to particle‐rotor calculations in which ani13/2proton is coupled to a triaxial core. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556638

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Three, possibly four, regularly spaced rotational bands with large dynamical moments of inertia, which are consistent with known superdeformed bands in the Lu/Hf region, have been identified in174Hf. The states were populated in the130Te(48Ca,4n) reaction at a beam energy of 194 MeV. The Gammasphere array detected the emitted gamma radiation. Ultimate cranker calculations predict substantial triaxial deformation (&ggr; ≈ ±17°) for highly deformed174Hf structures. However,174Hf is eight neutrons away from the previously establishedN= 94 triaxial superdeformed shell gap. Shell gaps atN= 100 and 106 with &ggr; ⩾ 15° are observed when &Vegr;2≈ 0.45, which may be responsible for the predicted TSD minima in174Hf. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556639

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A detailed spectroscopic study of high‐spin states in196Pb has been carried out using the EUROBALL spectrometer array. Five new magnetic‐rotational bands have been found and the previously known bands have been extended. With one exception, all the bands have been connected to lower‐lying states and excitation energies, spins and parities have been determined. Doppler‐broadend lineshapes have been analyzed and lifetimes of states in four of the bands have been determined. The B(M1) values show the decrease with increasing spin that is expected for shears bands. Configurations of proton‐particle excitations coupled to neutron‐hole states have been assigned to the bands. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556640

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

I shall first discuss the variations of magic numbers and shell structure in exotic nuclei by using effective single‐particle energies. An origin of these variations is shown to be the spin‐isospin dependent part of the nucleon‐nucleon interaction in nuclei. Such variations can be referred to as the shell evolution. As an outcome of this shell evolution in neutron‐rich exotic nuclei, magic numbers such asN=8, 20,etc.can disappear, whileN=6, 16,etc.arise. The shell gap is changed as a consequence of the shell evolution, and a good example is shown for30Na. An interesting case regarding shapes of exotic nuclei is presented for excitation energies andB(E2) values of32,34Mg exotic nuclei. It is suggested that various anomalous properties of exotic nuclei can be studied with the paradigm of shell evolution. In the second part, recent results of shell‐model studies will be presented for some Sn and Te nuclei. The anomalousB(E2) value of136Te can be explained within the shell model description which has described the spherical‐to‐deformed phase transition in Ba isotopes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556641

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We discuss an initial implementation of the coupled‐cluster method for nuclear structure calculations and apply our method to4He. We will discuss the future directions that this research will take as we move from method testing and development to more complete calculations. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556642

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Exact and approximate quantum numbers of the cranked Nilsson‐Strutinsky (CNS) formalism are exploited to calculate excited bands in fixed configurations with the energy of the individual bands minimized with respect to deformation for all spin values. The formalism is illustrated to calculate all bands which appear important in the decay out of the superdeformed band in59Cu. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556643

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The relativistic Hartree‐Bogoliubov (RHB) model is extended to include density dependent meson‐nucleon vertex functions. Compared with standard relativistic mean‐field effective interactions with nonlinear meson‐exchange terms, the density‐dependent meson‐nucleon couplings provide an improved description of asymmetric nuclear matter, neutron matter and nuclei far from stability. The relativistic random‐phase approximation is employed in the analysis of the evolution of the isovector dipole response in nuclei with large neutron excess, and of the dynamics of isoscalar dipole and compression modes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556644

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report on the low‐energy structure of the neutron‐rich, even‐even nuclides54Ti32,56Cr32, and58Cr34studied via &bgr;‐delayed &ggr;‐ray spectroscopy. The systematic variation of the excitation energy of first excited 2+states in the even‐even24Cr and22Ti isotopes provides evidence of a subshell closure atN= 32 for neutron‐rich nuclides having Z ⩽ 24. Shell model calculations, which correctly account for the appearance of theN= 32 subshell, also predict a new shell closure atN= 34 for Ti and Ca isotopes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1556645

出版商:AIP    

年代:1903

数据来源: AIP