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Statistical properties of the realistic energy spectra of the odd-odd nucleiAg,Au,Cs,K andRb, calculated within the Interacting Boson Fermion Fermion Model, are investigated by means of the Δ statistics and the Nearest Neighbor Spacing Distribution method. New probability distribution function, which describes well the calculated results and enables the characterization of chaos with a physically meaningfull parameter, is proposed. Level spacing fluctuations of the examined nuclei exhibit the transitional behavior between Poisson and GOE limits, revealing different degrees of chaoticity in their dynamics. [ABSTRACT FROM AUTHOR]

The level density of the odd-odd nucleus Pr is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes. The IBFFM total level density is fitted by a Gaussian and its tail is also fitted by Bethe formula and constant temperature Fermi gas model. The IBFFM spin-dependent level densities show high-spin reductions with respect to Bethe formula. This can be well accounted for by a modified spin-dependent level density formula. [ABSTRACT FROM AUTHOR]

Energy spectrum and electromagnetic properties ofPb have been studied in the cluster-vibration model (CVM). The lifetime of 0.3 ms was predicted for the 2.3 keV level which is of significance for considerations of theTl solar neutrino detector. [ABSTRACT FROM AUTHOR]

Large-scale combinatorial calculations of level densities were performed for selected nuclei using Gaussian polynomial generating function method (GPM). Contrary to the results of previous combinatorial calculations, we find a good agreement of the combinatorial total level densities and Bethe formula. Combinatorial GPM calculations were performed also for spin-dependent level densities and comparison is made with various algebraic formulas. On the basis of our GPM calculations we propose a new phenomenological spin-dependent level density formula, which in the low-spin limit reduces to the spin-dependent formula of Bethe. The new formula (24) is for all spins factorized into the product of total level density and spin distribution function, where the spin distribution function (25) contains an additional spin correction parameter. [ABSTRACT FROM AUTHOR]

Level density fluctuations are calculated within the generalized interacting boson model proposed for even-even nuclei, in dependence on the truncation parameter k. For the case ϰ=2 corresponding to the SU(3) dynamical symmetry of the interacting boson model the fluctuation pattern is close to Poissonian. For cases ϰ≠2, including the anharmonic vibrator model for which ϰ=∞, a rapid transition to the fluctuation pattern close to GOE is obtained. [ABSTRACT FROM AUTHOR]

Gamma rays ofAu obtained after double neutron capture inAu were measured at the ILL high flux reactor. A level scheme up to 1770 keV excitation energy is established. The result is compared with IBFM and Boson-Fermion-Symmetry calculations. [ABSTRACT FROM AUTHOR]

The properties of the triplet of low-lying states inMo have been studied through spectroscopy of the γ radiation following thermal neutron capture inMo and β decay ofNb and through a measurement of the proton angular distributions in theMo( d,p) reaction with 14 MeV deuteron energy. The half-lives of the 13.5 keV state and the 57.0 keV 5/2 state have been measured as 226(7) and 133(7)ns, respectively. These values and the quadrupole/dipole mixing ratios of the 13.5 keV and 43.5 keV transitions yield spin and parity 3/2 for the 13.5 keV level. The E2 components in the 13.5 (3/2 →1/2) and 43.5 keV (5/2→3/2) transitions are ≦ 8·10 and 54(9)%, respectively. The possibility of an additional state near to the 57.0 keV level is discussed. IBFM/PTQM calculations, taking into consideration the transitional character of theMo boson core, account for the electromagnetic-transition and transfer-reaction pattern of the triplet of states. [ABSTRACT FROM AUTHOR]

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A band with a rotational pattern based on a state at 585.1 keV has been identified in the N=59 neutron-rich nucleusSr. Its properties lead to the [422] 3/2 Nilsson-orbital assignment for the band head. There is evidence for a second band with the head at 644.7 keV and the configuration [541] 3/2. Since the ground state and the lowest excited levels are spherical, shape coexistence is established forSr. A deformed nature of several levels at 500-600 keV results also from QRPA-model calculations. The structure of the low-lying spherical levels has been studied in the frame of the IBF model. The results of the present investigations lead to a better understanding of the N=59 isotones which constitute the link between the spherical and deformed nuclei at A∼100 as a species with shape coexistence but without any indications of particular softness. [ABSTRACT FROM AUTHOR]

Spectral rigidity Δ ( L) is calculated for the energy spectra ofTe,Ba andCe, obtained in the IBFM calculation. Results reveal an intermediate situation between regularity and chaos, but remarkably closer to the chaotic limit. Influence of the model parameters on the fluctuation pattern is discussed. [ABSTRACT FROM AUTHOR]

A level scheme has been established forRb based on studies at the fission-product separator JOSEF of γγ coincidences following the β- decay ofKr. For the 190.7 keV level a half-life of 2.5(8) ns has been determined through the centroid-shift method. The major β-decay branch ofKr proceeds with log ft=3.7 into the 988.4 keV state inRb. This transition must be of the 0→1 GT type involving the transition νg→ πg. IBFFM calculations have been performed forRb, starting from the parametrization used in the previous IBM investigations for the isotopeRb and the isotoneY. A theoretical interpretation of the low-lying levels including propositions for the spins is given in a comparison to the available data. [ABSTRACT FROM AUTHOR]

The structure of the low-lying states with negative parity ofRb has been studied in the framework of the Interacting Boson-Fermion Model (IBFM) using the even-even neighbourSr as a core. A good description of the properties of the levels has been obtained. A sensitive test of the quality of the theoretical studies is the decay pattern of the second excited state at 267 keV with a half-life of 2.0(2) ns. The calculations give t=2.26 ns and they predict the existence of a 13 keV transition into the first excited state, the existence of which has been confirmed afterwards by experiments. [ABSTRACT FROM AUTHOR]

Unique-parity states ofY are studied in the framework of the interacting boson-fermion model (IBFM). Spin assignments for the levels of the unique-parity yrast band are proposed on the basis of nuclear systematics and the IBFM band pattern associated with coupling of a particle-type quasiparticle (g) to the SU(5) coreSr. The good fit of the experimental data with the IBFM calculations confirms the single particle character of this immediate neighbour of the doubly sub-magic nucleusZr. [ABSTRACT FROM AUTHOR]

The results of a γ-γ angular correlation and a low energy γ-ray singles measurement using thermal neutron capture inK are presented. The properties of low-lying levels ofK are interpreted in a comparison of the experimental data with the Interacting-Boson-Fermion-Fermion Model (IBFFM). The level fluctuation properties of the IBFFM spectrum are analysed and a sizeable deviation from chaoticity is found. [ABSTRACT FROM AUTHOR]

The structure of the nucleusY is discussed in the framework of the parabolic rule for the splitting of members of proton-neutron coupled configurations and of the interacting boson-fermion-fermion model (IBFFM). A good description of the available experimental data including the existence of the β decaying 8 isomer with a half-life of 10 s has been obtained which demonstrates the influence of the subshell closures in the neighbourhood ofZr. [ABSTRACT FROM AUTHOR]

In the Interacting Boson-Fermion-Fermion Model (IBFFM) for odd-odd nuclei the yrast states are calculated for $$\tilde j_\pi = \tilde h_{1 1/2} ,\tilde j_v = \tilde i_{1 3/2} $$ , proton-neutron configurations coupled to the O(6) and SU(3) boson core. The results are discussed in terms of the strongly coupled/ decoupled band type criterion and in comparison to the peaceful and conflicting case of asymmetric rotor model. [ABSTRACT FROM AUTHOR]

Ground state symmetric rotor bands are described as coherent-state structures of deformation in a quadrupole-phonon model. These structures are shown to be very different from the phonon composition of pseudobands which are culled from the excited state spectrum of nuclei such asSe,Kr, andKr. The pseudobands are shown to be only a subset of more complete excitation spectra, which occur in most unique-parity odd-nucleon nuclei with a transitional core and can be expected to occur throughout the chart of the nuclides. [ABSTRACT FROM AUTHOR]

The quantal analogs of the Gallagher-Moszkowski bands in the Interacting boson-fermion-fermion model (IBFFM) with SU (3) boson core are associated with the exact quantum number Kj+j and approximate quantum number K-¦ j-j¦ of IBFFM. For characteristic ratios Г/δ it is shown that the K=0 band in even-even IBM system, the K= j and K= j bands in the corresponding odd-even (IBFM) systems and the K= j+ j band in the corresponding odd-odd IBFFM system exhibit the supermultiplet pattern. [ABSTRACT FROM AUTHOR]

Life-times of low-lying levels inRb andRb have been determined from β−γ coincidence measurements at the fission-product separator JOSEF. Values of t=17.0(8) ns and 2.0(2) ns have been obtained for the levels at 1,134 keV inRb and 267 keV inRb, respectively, and upper limits could be deduced for several other states. Calculations in the frame of IBFM/PTQM have been performed forRb, the results of which allow an interpretation of the low-lying levels of this nucleus. For the 1,134 keV level the configuration [ πg⊗2] 7/2 is suggested which lies close to or even below the 9/2 level. The calculated half-life of 14 ns for the 1,134 keV level reproduces well the experimental value. The half-life of the 267 keV level inRb favours the assignment of I=1/2 to this state over the alternative 3/2. [ABSTRACT FROM AUTHOR]

The results obtained in this paper show that the SU(3) pattern in the spectra and transition rates of even-even nuclei appear qualitatively as a general feature of a large class of quadrupole-phonon models, independently of SU(3) symmetry. This pattern reflects the truncation of the quadrupole phonon space, incorporated via truncation operator in the fourth-order anharmonic quadrupole-phonon Hamiltonian. Three particular forms of the truncation operator are considered, corresponding to three models, namely the truncated quadrupole-phonon model (TQM), equivalent to the well-known interacting-boson model (IBM), the step-truncated quadrupole-phonon model (STQM), equivalent to a standard anharmonic quadrupole-phonon model and the linearly truncated quadrupole-phonon model (LTQM), introduced here. The results obtained provide a basis for a broader scope for the considerations in the SU(3) limit. [ABSTRACT FROM AUTHOR]

Low lying energy levels and transition probabilities ofZn are calculated in the Quasicluster-vibration model (QCVM). This model is an extension of the Clustervibration model (CVM) for three-particle-cluster vibration coupling. Instead of a three-particle cluster, now a one broken pair (number projected three quasiparticle) cluster is coupled to phonon states. It turns out that the sequence of isotopes may be described with one set of parameters, along the same line as previously used in the CVM. The resulting spectra and electromagnetic properties, for positive and negative parity states of odd Zn isotopes, compare with experimental data equally well as large shell-model calculations; this seems to justify the extension of the CVM to these nuclei with more than three particles or holes beyond a closed shell. [ABSTRACT FROM AUTHOR]

γ-spectra and excitation functions of theMo( p, nγ)Tc reaction were measured in the 1.2-3.6 MeV proton energy range by using thick, enriched targets, Ge(Li) and low energy photon (hyperpure Ge) spectrometers. These detectors were used in γγ-coincidence experiments, too. Conversion electron spectrum measurements were performed by means of a superconducting magnet transporter Si(Li) spectrometer (SMS) at E =4 MeV and multipolarities of some transitions have been determined. Based on the experimental results a level scheme ofTc has been constructed. Level energies ofTc were calculated on the basis of the parabolic rule, derived from the cluster-vibration model. [ABSTRACT FROM AUTHOR]

In the framework of the cluster-vibration model we discuss a quasi- f pattern of low-lying states inCe with the I=j-2 anomaly, and its consequences on the spectroscopic factors for this nucleus. [ABSTRACT FROM AUTHOR]

The properties of low-lying states inXe are described by coupling a three-neutronhole cluster to the quadrupole vibrational field. The results obtained by diagonalization of the model Hamiltonian and qualitative predictions based on Generalized Vibrational Intensity and Selection Rules (GVISR) are discussed. The results obtained in the present paper are compatible with recent experimental data onXe. Further experimental tests of the model are suggested. [ABSTRACT FROM AUTHOR]

The properties ofMo andMo nuclei, which are typical representatives of N=52 and N=53 nuclei, respectively, are described in the cluster-vibrational field coupling model in natural representation (without parameter fitting). The interplay of few valenceshell neutrons and vibrational degree of freedom gives rise to the coexistence of quasivibrational, quasirotational, and clustering phenomena. [ABSTRACT FROM AUTHOR]

Boson-fermion dynamical symmetry associated with U (5) boson core is introduced for odd-odd nuclei. An algorithm is constructed for the subsequent reduction appropriate for the boson-fermion group chain associated with an odd proton and neutron in j=3/2 configurations and the corresponding energy formula is given and exemplified forCu in the case of an associated supersymmetry. [ABSTRACT FROM AUTHOR]

Extrapolating the Interacting Boson-Model treatment from lighter neighbours toY we predict the properties of low-lying states of spherical nature in IBFFM. This odd-odd nucleus which presents one of the rare cases of coexisting spherical and deformed shapes is of fundamental importance for understanding nuclear phase transitions. [ABSTRACT FROM AUTHOR]

The K=3/2 rotational band has been identified inY with a band-head energy of 536 keV. This result is in contradiction with previously reported data, but is in agreement with predictions of the IBFM/PTQM model. [ABSTRACT FROM AUTHOR]

The levels ofAu have been calculated in IBFFM as a first application of the new model for odd-odd nuclei. The study of the Au (n, γ) spectrum has led to a large amount of data on the odd-odd nucleusAu, with spin/parity assignments of numerous low-lying states /l/. In particular, fifteen 1, 2 levels have been found below 500 keV. However, at that time a detailed comparison with nuclear structure theory was not possible. In last decade, the interacting boson model was extensively applied to description of even-even and odd-even nuclei /2,3/. Only recently, this approach was extended to odd-odd nuclei /4-8/. A new model /4,5/ for odd-odd nuclei was introduced, referred to as IBFFM or OTQM. In related development, a few dynamical symmetries and supersymmetries have been introduced, which encompass odd-odd nuclei. These supersymmetries are associated with U (6/4)×U (6/4) /6/, U(6/12)×U (6/4) /7/ and with a symplectic chain /8/. [ABSTRACT FROM AUTHOR]

Boson-fermion dynamical symmetry is introduced for hypernuclei with odd proton, odd neutron and hyperon in j=3/2 configurations and with SO(6) boson core. [ABSTRACT FROM AUTHOR]

In TQM a Δn=2 term is introduced in the two-particle transfer operator, which gives a sizeable shift of the L=0 transfer strength to the excited 0 state in SU(3) and SU(5) limits of IBM/TQM. [ABSTRACT FROM AUTHOR]

We introduce the SU(6) model IBOM/OTQM for odd-odd nuclei and discuss the bands in O(6) limit. Bands are characterized by a particular type of phase correlations in the wave functions and exhibit splitting of the SU(3) analogs of Gallagher-Moszkowski bands. [ABSTRACT FROM AUTHOR]

For odd-odd nuclei we introduce three dynamical boson-fermion symnetries associated with j=3/2, j=3/2 and U(5) symmetry of the boson core. The corresponding energy formulas and quantum numbers for low-lying states are explicitly given. [ABSTRACT FROM AUTHOR]