475 research outputs found
Rotational alignment near N=Z and proton-neutron correlations
The effects of the residual proton-neutron interactions on bandcrossing
features are studied by means of shell model calculations for nucleons in a
high-j intruder orbital. The presence of an odd-nucleon shifts the frequency of
the alignment of two nucleons of the other kind along the axis of rotation. It
is shown that the anomalous delayed crossing observed in nuclei with aligning
neutrons and protons occupying the same intruder subshell can be partly
attributed to these residual interactions.Comment: 14 pages, including 5 eps figures submitted to Phys. Rev.
Covariant density functional theory for antimagnetic rotation
Following the previous letter on the first microscopic description of the
antimagnetic rotation (AMR) in 105Cd, a systematic investigation and detailed
analysis for the AMR band in the frame-work of tilted axis cranking (TAC) model
based on covariant density functional theory are carried out. After performing
the microscopic and self-consistentTAC calculations with an given density
functional, the configuration for the observed AMR band in 105Cd is obtained
from the single-particle Routhians. With the configuration thus obtained, the
tilt angle for a given rotational frequency is determined self-consistently by
minimizing the total Routhian with respect to the tilt angle. In such a way,
the energy spectrum, total angular momenta, kinetic and dynamic moments of
inertia, and the B(E2) values for the AMR band in 105Cd are calculated. Good
agreement with the data is found. By investigating microscopically the
contributions from neutrons and protons to the total angular momentum, the
"two-shears-like" mechanism in the AMR band is clearly illus-trated. Finally,
the currents leading to time-odd mean fields in the Dirac equation are
presented and discussed in detail. It is found that they are essentially
determined by the valence particles and/or holes. Their spatial distribution
and size depend onthe specific single-particle orbitals and the rotational
frequency.Comment: 35 pages, 17 figures, accepted by Phys. Rev.
Symmetry Breaking by Proton-Neutron Pairing
The symmetries of the and pair-fields are different. The
consequences for rotational spectra are discussed. For , the concept of
spontaneous breaking and subsequent restoration of the isospin symmetry turns
out to be important. It permits us to describe the proton-neutron
pair-correlation within the conventional frame of pairing between like
particles. The experimental data are consistent with the presence of a
field at low spin in nuclei. For a substantial field, the
spectra of even-even and odd-odd nuclei become similar. The
possibility of a rotationally induced pair-field at high spin is
considered.Comment: 7 pages 9 figure
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