Lifetimes of states in ${}_{}{}^{82}{}_{}{}^{}\mathrm{Y}$ and ${}_{}{}^{82}{}_{}{}^{}\mathrm{Sr}$ produced by the ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^{27}$Al,2pn${)}^{82}$Y and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$${(}^{27}$Al,3p${)}^{82}$Sr reactions at 90 MeV have been measured using the recoil distance method. The present results along with previous measurements show how the B(E2) strengths and collectivity vary with spin in the lowest π=+ and π=- bands of ${}_{}{}^{82}{}_{}{}^{}\mathrm{Y}$ and in the ground state band of ${}_{}{}^{82}{}_{}{}^{}\mathrm{Sr}$. The alternating pattern of B(M1) strengths in the yrast band of ${}_{}{}^{82}{}_{}{}^{}\mathrm{Y}$ has been confirmed. © 1996 The American Physical Society.

Excited states in the doubly-${\mathrm{odd}}^{184}$Au nucleus have been studied by in-beam γ-ray spectroscopy. This nucleus was produced through the fusion-evaporation reactions ${}_{}{}^{165}{}_{}{}^{}\mathrm{Ho}$${(}^{24}$Mg, 5n), ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$${(}^{19}$F, 5n), and ${}_{}{}^{161}{}_{}{}^{}\mathrm{Dy}$${(}^{27}$Al, 4n). Different rotational band structures have been observed and interpreted as specific couplings of proton and neutron single-particle excitations present in neighboring odd Au and Pt nuclei. © 1996 The American Physical Society.

Tellurobismuthite (${\mathrm{Bi}}_2$${\mathrm{Te}}_3$) has been analyzed for Xe isotopes to determine the half-life for double-β decay of ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$. Excess ${}_{}{}^{130}{}_{}{}^{}\mathrm{Xe}$ amounts to (6.18±0.18)×${10}^7$ atom/g with 47.8 wt. % Te, or (1.24±0.04)×${10}^{13}$ for the parent/daughter ratio ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$${/}^{130}$Xe. With (9.3±1.1)×${10}^7$ yr for the Xe retention age of Te mineral, this provides (7.9±1.0)×${10}^{20}$ yr for the absolute half-life of ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ double-β decay. With this and a literature ratio ${\mathit{T}}_{1/2}$(130)/${\mathit{T}}_{1/2}$(128) of (3.52±0.11)×${10}^{\mathrm{-}4}$, we have (2.2±0.3)×${10}^{24}$ yr for the absolute half-life of ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ double-β decay. © 1996 The American Physical Society.

High-spin states up to I∼20ħ have been studied in the ${}_{}{}^{121,122}{}_{}{}^{}\mathrm{Te}$ nuclei using the ${}_{}{}^{116}{}_{}{}^{}\mathrm{Cd}$${(}^9$Be,xn) reaction at 37.8 MeV. In this spin regime, several favored noncollective oblate states (γ=+60°), where the single-particle angular momenta generate the total nuclear spin, are predicted to coexist with weakly deformed collective structures. Theoretical expectations for such oblate states, based on TRS cranking calculations, are compared to the experimental results. © 1996 The American Physical Society.

Assuming axial symmetry of the nuclear shape and the Skyrme force SIII updated on the pairing interaction ${\mathit{V}}_0$δ(r${\to }_{12}$) we performed constrained Hartree-Fock calculations of well deformed even gadolinium ${}_{64}{}^{}{}_{}{}^{}\mathrm{Gd}$ isotopes with neutron numbers N=86–106. The mass spectrum, nuclear radii, neutron skin thickness, quadrupole moments (deformations), and low-spin rotational levels are calculated. In all the cases viewed the angular momentum projection after variation was performed. This was achieved by explicit inclusion of the rotational energy -〈?${\mathrm{^}}^2$〉/2J. The procedure corrects the ground state deformations and gives deformations and energies of low excited states as well. The results found have all been compared to experimental data. © 1996 The American Physical Society.

An unresolved issue in the present understanding of nucleon structure is the effect of hidden strangeness on electromagnetic observables such as ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$(${\mathit{q}}^2$). Previously, we have shown that ${\mathit{G}}_{\mathit{E}}^{\mathit{n}}$(${\mathit{q}}^2$) is sensitive to small φNN couplings. A complementary approach for understanding effects due to strangeness content and the Okubo-Zweig-Iizuka (OZI) rule is to investigate the electromagnetic structure of hyperons. We apply Sakurai’s universality limit of the SU(3${)}_{\mathit{F}}$ symmetry relations and a prescription based on the OZI rule to calculate the electromagnetic form factors of the baryon octet states (p,n,Λ,${\mathrm{\Sigma }}^{+}$,${\mathrm{\Sigma }}^0$,${\mathrm{\Sigma }}^{\mathrm{-}}$,${\mathrm{\Xi }}^0$,${\mathrm{\Xi }}^{\mathrm{-}}$) within the framework of an extended vector meson dominance model. To provide additional motivation for experimental investigation, we discuss the possibility of extracting the ratio ${\mathit{G}}_{\mathit{M}}^{\mathrm{\Lambda }}$(${\mathit{q}}^2$)/${\mathit{G}}_{\mathit{M}}^{\mathrm{\Sigma }\mathrm{\Lambda }}$(${\mathit{q}}^2$) from the Λ/Σ polarization ratio in kaon electroproduction experiments. © 1996 The American Physical Society.

We search for three-neutron resonances which were predicted from pion double charge exchange experiments on ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. All partial waves up to J=5/2 are nonresonant except the ${\mathit{J}}^{\mathrm{\pi }}$=3/$2^{+}$ one, where we find a state at E=14 MeV energy with 13 MeV width. The parameters of the mirror state in the three-proton system are E=15 MeV and Γ=14 MeV. The possible existence of an excited state in the triton, which was predicted from a H${(}^6$He,α) experiment, is also discussed. © 1996 The American Physical Society.

For the first forbidden unique (1u) radiative electron-capture β decay of ${}_{}{}^{41}{}_{}{}^{}\mathrm{Ca}$, a contribution of the γ/β detour transitions via virtual nuclear states to the bremsstrahlung spectrum has been considered in terms of the shell model. Calculations of the matrix elements for the virtual E1 γ and allowed Gamow-Teller β transitions have been performed with the use of the Warburton, Becker, Millener, and Brown interactions. For the effective charge, which describes the contribution of the detour transitions, an interval 0.96<${\mathit{e}}_{\mathrm{eff}}$<1 has been found. The model predictions are fairly close to the experimental value ${\mathit{e}}_{\mathrm{eff}}$=0.78. A possible origin of the small remaining deviation is discussed. © 1996 The American Physical Society.

The effect of short-range correlations (SRC) on Ca isotopes is studied using a simple phenomenological model. Theoretical expressions for the charge (proton) form factors, densities, and moments of Ca nuclei are derived. The role of SRC in reproducing the empirical data for the charge density differences is examined. Their influence on the depletion of the nuclear Fermi surface is studied and the fractional occupation probabilities of the shell model orbits of Ca nuclei are calculated. The variation of SRC as function of the mass number is also discussed. © 1996 The American Physical Society.

Nuclear models predict a redistribution of the intraband-interband E2 strength related to low-spin yrast states when the mean shape asymmetry 〈γ〉 varies with spin. Thereby, a reduction of the yrast intraband E2 strength may result. Possible evidence for such a reduction is observed in ${}_{}{}^{128}{}_{}{}^{}\mathrm{Ba}$ and is interpreted as a variation of the shape asymmetry 〈γ〉 with increasing spin. © 1996 The American Physical Society.

Alpha spectroscopic factors for quartet wave functions are recalled for identical chains, which correspond to positive natural parity states. A generalization is presented for nonidentical chains which can give rise to negative natural parity states. Applications to the 0f-1p shell quartet structures observed in the ${(}^{16}$O${,}^{12}$C) and ${(}^6$Li,d) reactions are given for the population of the first $2^{+}$ excited state and for the population of low-lying $3^{\mathrm{-}}$ excited states. © 1996 The American Physical Society.

The interacting boson model is extended by the inclusion of selective noncollective fermion states through the successive breaking of the correlated S and D pairs (s and d bosons). High angular momentum states are generated in this way, and their structure described by the coupling between fermions in broken pairs and the boson core. The model space of bosons and broken pairs contains also unphysical states that are generated automatically when fermions couple to angular momenta ${\mathit{J}}_{\mathit{F}}$=0 and 2. A procedure is derived for the projection of spurious components from bases that contain one fermion pair. Spurious states are identified and an algorithm for their projection is constructed. The model is applied to the description of states in the spherical nucleus ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$, and the weakly deformed nucleus ${}_{}{}^{82}{}_{}{}^{}\mathrm{Sr}$. Calculated spectra and transition probabilities are compared with experimental data. It is found that projection of spurious states from the model space is essential for a description of excited states with low angular momenta above the yrast, while it is less important for high-spin states close to the yrast line. © 1996 The American Physical Society.

The vibrating potential model, which represents a self-consistent version of the random-phase approximation (RPA) with a separable residual interaction, is generalized to the description of Eλ collective excitations in nuclei with any even-multipole static deformation. The model is used to study the isoscalar E2 and E3 giant resonances in deformed and superdeformed ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ and ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$. The importance of the nuclear self-consistency is shown. The model provides a satisfactory description of the isoscalar E2 and E3 giant resonances in deformed ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$, predicting a considerable washing out of these resonances, especially the octupole one, in superdeformed ${}_{}{}^{152}{}_{}{}^{}\mathrm{Dy}$. The latter result means that the experimental observation of the isoscalar giant resonance in superdeformed nuclei can encounter serious troubles. © 1996 The American Physical Society.

A new mode of internal conversion decay, in which the converted electron is excited to a bound orbital instead of a continuum orbital, is discussed. General theoretical results are presented for the relation between bound internal conversion and continuum internal conversion of the nucleus. It is shown that the transition rate for internal conversion decay is continuous across the energy threshold between continuum final states and bound final states. Theoretical predictions for decay to bound states of ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}$ are consistent with experimental data on internal conversion in highly charged ions of this nuclide. © 1996 The American Physical Society.

The introduction of an adequate auxiliary space allows us to replace the problem of the treatment of coupled phonons, which is very complicated and voluminous, with the problem of the treatment of usual matrices. As applications of this approach, the formulation of a Wick’s theorem for coupled phonons and recursion formulas which can be used to calculate the overlap matrix elements of multiphonon states built with n coupled phonons of different types and collectivities are given. © 1996 The American Physical Society.

In a previous paper a semimicroscopic core-particle coupling method that includes the conventional strong coupling core-particle model as a limiting case was applied to spectra and electromagnetic properties of several well-deformed odd nuclei. This work coupled a large single particle space to the ground-state bands of the neighboring even cores. In this paper, we generalize the theory to include excited bands of the cores, such as β and γ bands, and thereby show that the resulting theory can account for the location and structure of all bands up to about 1.5 MeV. © 1996 The American Physical Society.

‘‘Effective’’ γ-deformation parameters are derived for even-even Xe, Ba, and Ce nuclei from the matrix elements of (Q×Q${)}_{00}$ and (Q×Q×Q${)}_{00}$. Interacting boson model calculations are performed with the quadrupole operator Q determined from the E2 branching ratios of the $2_2^{+}$ decay and compared to results obtained with the rigid triaxial rotor model. © 1996 The American Physical Society.

It is shown that the norm corrections, introduced to avoid the violation of the constraints on the depletion of the hole states in the standard perturbative 2p2h approach, leads in nuclear matter to a dependence of the momentum distribution with the total nucleon number. This unphysical behavior, which in turn makes the depletion to be nonextensive, arises from contributions of disconnected diagrams contained in the norm. It is found that the extensivity is again recovered when the 4p4h excitations in the ground state are included, and a reasonable value for the total number of nucleons promoted above the Fermi level is obtained. © 1996 The American Physical Society.

The surface and curvature properties of semi-infinite polarized nuclear matter (SPNM) are calculated using an expansion for the Fermi integrals up to ${\mathit{T}}^2$. A density matrix expansion is obtained for a modified form of the Seyler-Blanchard interaction. New parameters that characterize the surface and curvature properties of SPNM are introduced. The level density parameter is extracted from the low temperature expansion of the free energy and compared with previous calculations. A reasonable agreement is obtained with the parameters calculated before. © 1996 The American Physical Society.

Wave functions of sd interacting boson with definite F spin are constructed explicitly according to the group chain U(2N)⊃[U(N)⊃O(N)⊃O(3)]⊗SU(2). The model space is truncated with the restriction F=${\mathit{F}}_{\max }$ and F=${\mathit{F}}_{\max }$-1. The model wave functions are used to calculate the energy levels, B(E2) values and B(M1) values for the F-spin multiplet ${}_{}{}^{184}{}_{}{}^{}\mathrm{W}$, ${}_{}{}^{184}{}_{}{}^{}\mathrm{Os}$, ${}_{}{}^{184}{}_{}{}^{}\mathrm{Pt}$, and ${}_{}{}^{184}{}_{}{}^{}\mathrm{Hg}$. It was found that the energy spectra can be reproduced quite well and the B(E2) and B(M1) values can be reproduced reasonably well. The F-spin configuration characteristics of the energy eigenfunctions are discussed. The truncation scheme is an efficient way to reduce the model space of IBA-2 and can be extensively employed to do practical calculations in the framework of IBA-2. © 1996 The American Physical Society.