1,052 research outputs found

### Proton-neutron symmetry in 92Zr, 94Mo with Skyrme interactions in a separable approximation

Starting from a Skyrme interaction we study the properties of the low-energy
spectrum of quadrupole excitations in 90,92Zr, 92,94Mo. The coupling between
one- and two-phonon terms in the wave functions of excited states are taken
into account. We use the finite-rank separable approximation which enables one
to perform the QRPA calculations in very large two-quasiparticle spaces. Our
results from the SGII Skyrme interaction in connection with the volume pairing
interaction are in reasonable agreement with experimental data. In particular,
we present the successful description of the M1 transition between low-energy
quadrupole excitations.Comment: 9 pages, 3 figure

### Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near spherical nuclei

The interrelation between the octupole phonon and the low-lying
proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei is
investigated. The one-phonon states decay by collective E3 and E2 transitions
to the ground state and by relatively strong E1 and M1 transitions to the
isoscalar 2+ state. We apply the proton-neutron version of the Interacting
Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin
symmetric dynamical symmetry limits of the model, namely the vibrational and
the \gamma-unstable ones, are considered. We derive analytical formulae for
excitation energies as well as B(E1), B(M1), B(E2) and B(E3) values for a
number of transitions between low-lying states.Comment: 25 pages, 3 figures, LaTeX, epsfig. Nucl. Phys. A (in press

### Quadrupole shape invariants in the interacting boson model

In terms of the Interacting Boson Model, shape invariants for the ground
state, formed by quadrupole moments up to sixth order, are studied in the
dynamical symmetry limits and, for the first time, over the whole structural
range of the IBM-1. The results are related to the effective deformation
parameters and their fluctuations in the geometrical model. New signatures that
can distinguish vibrator and gamma-soft rotor structures, and one that is
related to shape coexistence, are identified.Comment: 10 pages, ReVTeX, epsf, 2 Postscript figures include

### Transition Rates between Mixed Symmetry States: First Measurement in 94Mo

The nucleus 94Mo was investigated using a powerful combination of
gamma-singles photon scattering experiments and gamma-gamma-coincidence studies
following the beta-decay of 94mTc. The data survey short-lived J^pi=1+,2+
states and include branching ratios, E2/M1 mixing ratios, lifetimes, and
transition strengths. The mixed-symmetry (MS) 1+ scissors mode and the 2+ MS
state are identified from M1 strengths. A gamma transition between MS states
was observed and its rate was measured. Nine M1 and E2 strengths involving MS
states agree with the O(6) limit of the interacting boson model-2 using the
proton boson E2 charge as the only free parameter.Comment: 9 pages, 3 PostScript figures included, ReVTeX, accepted for
publication in Physical Review Letters, tentatively scheduled for August 9,
199

### Simple relations among E2 matrix elements of low-lying collective states

A method is developed to derive simple relations among the reduced matrix
elements of the quadrupole operator between low-lying collective states. As an
example, the fourth order scalars of Q are considered. The accuracy and
validity of the proposed relations is checked for the ECQF Hamiltonian of the
IBM-1 in the whole parameter space of the Casten triangle. Furthermore these
relations are successfully tested for low-lying collective states in nuclei for
which all relevant data is available.Comment: 12 pages, 1 figure, RevTeX preprint-styl

### Isovector multiphonon excitations in near spherical nuclei

The lowest isoscalar and isovector quadrupole and octupole excitations in
near spherical nuclei are studied within the the proton-neutron version of the
interacting boson model including quadrupole and octupole bosons (sdf-IBM-2).
The main decay modes of these states in near spherical nuclei are discussed.Comment: 4 pages, 1 figure, LaTeX, sprocl, epsfig. Proc. Int. Conf. on
Structure of the Nucleus at the Dawn of the Century (Bologna, 29 May - 3 June
2000); in pres

### Gamma-soft Analog of the Confined Beta-soft Rotor Model

A gamma-soft analog of the confined beta-soft (CBS) rotor model is developed,
by using a gamma-independent displaced infinite well beta-potential in the Bohr
Hamiltonian, for which exact separation of variables is possible. Level schemes
interpolating between the E(5) critical point symmetry (with R(4/2)=E(4)/E(2)=
2.20) and the O(5) gamma-soft rotor (with R(4/2)=2.50) are obtained, exhibiting
a crossover of excited 0+ bandheads which leads to agreement with the general
trends of first excited 0+ states in this region and is observed experimentally
in 128-Xe and 130-Xe.Comment: 10 pages, LaTeX, including 7 eps figure

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