[en] An elementary account is given of the neutron-proton interacting boson model (IBA-2). Emphasis is on the phenomenological and qualitative aspects of the model, particularly in relation to IBA-1. Young tableaux are introduced for classification of wave function symmetries. The generalized Bose principle is introduced for the construction of complete IBA-2 wave functions. Proton-neutron symmetry with associated F spin and Majorana force is studied in terms of simple examples [U(5) limit and small boson numbers?. E2 and M1 matrix elements and selection rules are worked out in detail. The numerical application is discussed. (author)

[en] Theoretical estimates for isospin-forbidden beta-delayed proton and two-proton emission are calculated in a shell-model framework. The parent nuclei studied are ²³Al and ³¹Ar. The results are compared to new experimental data. The reliability of the shell-model estimates is discussed

No abstract available

[en] Multipole mixing ratios of gamma rays serve as a sensitive probe of nuclear structure. Directional measurements, mostly by γγ angular correlation and nuclear orientation, yield the mixing ratios delta with sign. Unfortunately the results are often double valued. Furthermore, comparison between experimental and theoretical conversion coefficients can give |delta|. The E2/M1 mixing ratio delta(E2/M1) is of special importance in studying collective phenomena and models for their description. Present study is carried out mostly in terms of IBA-1, which makes no distinction between proton and neutron bosons

No abstract available

[en] The interacting-boson model of nuclear structure is presented in its basic version (IBA-1). Its group-theoretical structure is explained largely in terms of the analogue to angular-momentum theory. The dynamic symmetries U(5) (spherical vibrator), SU(3) (rigid rotor) and O(6) (γ unstable) are emphasized as special cases. The excitation energies and B(E2) values are worked out in detail for the simplest nontrivial case N = 3. Comparison with the Bohr-Mottelson model is made particularly for ¹⁶⁸Er. The proton-neutron boson model (IBA-2), the boson-fermion model for odd nuclei (IBFA) and the super symmetries connecting even and odd nuclei are briefly discussed

No abstract available

[en] The IBA-1 version of the interacting boson model with four energy parameters and the projection model (PM) with two (isotropic) or four (anisotropic) energy parameters are applied to sup(150-160)Gd nuclear structure data. It is shown that neither simple collective model used gives an adequate description of near-doubly-magic ₁₅₀Gd though both models describe the general band-head trends. The PM is clearly better than the IBA in accounting for unadiabatic details within the quasi-rotational bands. The IBA unlike the PM reproduces the observed weak ß-to-ground coupling and both models give a fair description of E2 branching ratios. The constancy of the IBA E2 operator for deformed nuclei is valid and the models show the N = 88-90 shape transition in parameter discontinuities. (U.K.)

No abstract available

[en] The interacting-boson model (IBM≡IBA) of nuclear structure is reviewed. Its phenomenological basic version IBA-1 is discussed as a numerical scheme and in terms of its group structure and dynamic symmetries. The proton-neutron version IBA-2 is considered both as a phenomenological model and as an approximation to the shell model. Dynamic symmetries, F spin and magnetic phenomena are examined. The microscopic basis of the IBA is viewed within the Otsuka-Arima-Iachello mapping scheme. 54 refs