摘要:

The interacting boson model is first defined mathematically and then its two possible physical interpretations are discussed. The role of the neutron/proton degree of freedom is described. Brief mention is made of the extension to odd nuclei and finally an example of the mapping from a shell model calculation onto tne IBM is given.

ISSN:0094-243X    

DOI:10.1063/1.35127

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The microscopic basis of the Interacting Boson Model is discussed. The IBM Hamiltonian is constructed microscopically in the following two steps. In the first step, the collective nucleon pairs of J=0+(S), 2+(D), etc. are mapped onto the corresponding bosons. Nucleon‐nucleon interactions are also mapped onto boson‐boson interactions. The mapping method for spherical nuclei is reviewed, and the mapping method for deformed nuclei, which was recently developed, is discussed in some detail. Low‐lying collective states primarily consist of S and D pairs. Consequently, the corresponding boson states mainly consist of s and d bosons, while there are some admixture of g‐bosons. In the second step of the derivation of the IBM Hamiltonian, effects of these g‐bosons are included within the s‐d boson space by a unitary transformation which transforms a combination of d and g bosons into a new d‐boson. It is demonstrated that the s‐d Hamiltonian thus derived indeed reproduces spectra of the original s‐d‐g Hamiltonian.

ISSN:0094-243X    

DOI:10.1063/1.35035

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Although the IBA‐1 contains no solutions corresponding to a rigid triaxial shape, it does contain an effective asymmetry arising from zero point motion in a &ggr;‐soft potential leading to a non‐zero mean or rms &ggr;. In the Consistent Q Formalism (CQF) of the IBA, most results of a calculation depend only on one parameter &khgr;. A relation will be established between &khgr; and the effective asymmetry parameter &ggr;. The relation between the asymmetry occurring naturally in IBA‐1 and the triaxiality arising from the introduction of cubic terms into the IBA Hamiltonian will be discussed. It will be shown that &ggr;‐band energy staggering is a particularly sensitive indicator of the degree of &ggr; rigidity. Finally, an extensive new region of 0(6) like Xe and Ba nuclei near A=130 will be discussed. Their remarkable similarity to Pt will be explored. Deviations from the strict 0(6) limit can be described in terms of the interplay of soft and rigid axial asymmetry and calculations will be presented that interpret the Xe, Ba and Pt isotopes in this way.

ISSN:0094-243X    

DOI:10.1063/1.35028

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Several experimental results have recently raised again the problem of the description of the anharmonicities of the vibrations observed in even‐even deformed nuclei.

ISSN:0094-243X    

DOI:10.1063/1.35123

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Dynamical supersymmetry in nuclei is derived from the U(6) symmetry of the IBA. Examples of calculated level schemes for197Au,196Pt,198Pt, and199Pt are compared with experimental results. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.35088

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A new particle‐core basis having approximate supersymmetric (SUSY) features associated with SU(3) dynamical symmetry is introduced. The SUSY and CO‐SUSY limits of IBFM/PTQM appear for the characteristic intermediate coupling strengths &Ggr;/&dgr;=±(&Ggr;/&dgr;)SUSY. The CO‐SUSY limit is a truncated analog of the Stephens rotation‐aligned scheme. A paradox was found in the relation of the SUSY and truncated strong coupling (TSC) limits to the strong coupling limit of the Bohr‐Mottelson model.Microscopic dyson and Holstein‐Primakoff realizations of RPA collective quadrupole phonon operators are explicitly constructed. Employing this mapping procedure in conjunction with the leading RPA diagrams, various operators of IBM/TQM, IBFM/PTQM have been derived in the particle‐hole channel: E2 operator, one‐particle transfer operator, two‐particle transfer operator etc. In addition to the standard terms, this derivation gives in the same diagrammatic order the additional terms also.A new model was introduced for the odd‐odd nuclei in the framework of IBM/TQM. For the SU(3) core the truncated analog of Gallagher‐Moszkowski bands appears as the approximate SUSY pattern, of the same intrinsic structure as in the odd‐even system.The idea of boson‐fermion dynamical symmetry and supersymmetry is extended to odd‐odd nuclei and hypernuclei.

ISSN:0094-243X    

DOI:10.1063/1.35071

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Current techniques make it possible to carry out shell‐model calculations which incorporate several single‐particle orbits and hundreds to thousands of different combinations of particle distribution and spin coupling for a given nuclear state. We review briefly the current status of the ‘‘technology’’ of such calculations. We then consider in some detail one example of current work, in which wave functions for all sd‐shell nuclear states have been obtained from a shell‐model calculation which employs an empirical Hamiltonian and the complete set of 0d5/2‐1s1/2‐0d3/2 basis vectors. We examine the electromagnetic matrix elements calculated from these wave functions in a variety of contexts to demonstrate how this theoretical approach works and to elluminate important issues in current nuclear structure research.

ISSN:0094-243X    

DOI:10.1063/1.35048

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

By the use of &Dgr;3and &sgr;2(k) statistics a comparison is made between the fluctuation properties of a two‐body random boson ensemble and the Gaussian orthogonal ensemble (GOE). With the two statistics no significant differences between the two ensembles have been found.

ISSN:0094-243X    

DOI:10.1063/1.35032

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown that the 2+level at about 2 MeV in the N=84 isotones140Ba,142Ce and144Nd may be identified as the lowest state of mixed symmetry in the U(5) limit of the IBM‐2.

ISSN:0094-243X    

DOI:10.1063/1.35033

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The properties of the magnetic octopole operator are discussed in the framework of the neutron‐proton Interacting Boson model. It is predicted that in deformed nuclei the I&pgr;=3+member of a low‐lying collective K=1+band can be excited with an appreciable strength.

ISSN:0094-243X    

DOI:10.1063/1.35034

出版商:AIP    

年代:1985

数据来源: AIP