804 research outputs found
Potential energy surfaces of actinide and transfermium nuclei from multi-dimensional constraint covariant density functional theories
Multi-dimensional constrained covariant density functional theories were
developed recently. In these theories, all shape degrees of freedom
\beta_{\lambda\mu} deformations with even \mu are allowed, e.g., \beta_{20},
\beta_{22}, \beta_{30}, \beta_{32}, \beta_{40}, \beta_{42}, \beta_{44}, and so
on and the CDFT functional can be one of the following four forms: the meson
exchange or point-coupling nucleon interactions combined with the non-linear or
density-dependent couplings. In this contribution, some applications of these
theories are presented. The potential energy surfaces of actinide nuclei in the
(\beta_{20}, \beta_{22}, \beta_{30}) deformation space are investigated. It is
found that besides the octupole deformation, the triaxiality also plays an
important role upon the second fission barriers. The non-axial
reflection-asymmetric \beta_{32} shape in some transfermium nuclei with N =
150, namely 246Cm, 248Cf, 250Fm, and 252No are studied.Comment: 7 pages, 6 figures; invited talk at the International Conference on
Nuclear Structure and Related Topics, Jul 02-July 7, 2012, Dubn
Microscopic and self-consistent description for neutron halo in deformed nuclei
A deformed relativistic Hartree-Bogoliubov theory in continuum has been
developed for the study of neutron halos in deformed nuclei and the halo
phenomenon in deformed weakly bound nuclei is investigated. Magnesium and neon
isotopes are studied and some results are presented for the deformed
neutron-rich and weakly bound nuclei 44Mg and 36Ne. The core of the former
nucleus is prolate, but the halo has a slightly oblate shape. This indicates a
decoupling of the halo orbitals from the deformation of the core. The generic
conditions for the existence of halos in deformed nuclei and for the occurrence
of this decoupling effect are discussed.Comment: 7 pages, 2 figures; invited talk at the XXXV Brazilian Workshop on
Nuclear Physics, Sep 2-6, 2012, Maresias, Brazi
Halos in a deformed Relativistic Hartree-Bogoliubov theory in continuum
In this contribution we present some recent results about neutron halos in
deformed nuclei. A deformed relativistic Hartree-Bogoliubov theory in continuum
has been developed and the halo phenomenon in deformed weakly bound nuclei is
investigated. These weakly bound quantum systems present interesting examples
for the study of the interdependence between the deformation of the core and
the particles in the halo. Magnesium and neon isotopes are studied and detailed
results are presented for the deformed neutron-rich and weakly bound nuclei
42Mg. The core of this nucleus is prolate, but the halo has a slightly oblate
shape. This indicates a decoupling of the halo orbitals from the deformation of
the core. The generic conditions for the existence of halos in deformed nuclei
and for the occurrence of this decoupling effect are discussed.Comment: 6 pages, 2 figures; invited talk at the 2nd Int. Conf. on Nuclear
Structure & Dynamics (NSD12), Opatija, Croatia, 9-13 July 201
Multidimensionally-constrained relativistic mean-field study of triple-humped barriers in actinides
Potential energy surfaces (PES's) of actinide nuclei are characterized by a
two-humped barrier structure. At large deformations beyond the second barrier
the occurrence of a third one was predicted by Mic-Mac model calculations in
the 1970s, but contradictory results were later reported. In this paper,
triple-humped barriers in actinide nuclei are investigated with covariant
density functional theory (CDFT). Calculations are performed using the
multidimensionally-constrained relativistic mean field (MDC-RMF) model, with
functionals PC-PK1 and DD-ME2. Pairing correlations are treated in the BCS
approximation with a separable pairing force of finite range. Two-dimensional
PES's of Th and U are mapped and the
third minima on these surfaces are located. Then one-dimensional potential
energy curves along the fission path are analyzed in detail and the energies of
the second barrier, the third minimum, and the third barrier are determined.
DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and
U. The third minima in Th are very shallow, whereas those
in Th and U are quite prominent. With PC-PK1 a third
barrier is found only in Th. Single-nucleon levels around the
Fermi surface are analyzed in Th, and it is found that the formation of
the third minimum is mainly due to the proton energy gap at and . The possible occurrence of a third
barrier in actinide nuclei depends on the effective interaction used in
multidimensional CDFT calculations. More pronounced minima are predicted by the
DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third
well in Th isotopes decreases with increasing neutron number. The origin of the
third minimum is due to the proton shell gap at relevant deformations.Comment: 10 pages, 7 figures; Phys. Rev. C, in press; due to the limitation
"The abstract field cannot be longer than 1,920 characters", the abstract
appearing here is slightly shorter than that in the PDF fil
A multi-wavelength observation and investigation of six infrared dark clouds
Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet
they play a crucial role in breeding newly-formed stars.
Aims. With the aim of further understanding the dynamics, chemistry, and
evolution of IRDCs, we carried out multi-wavelength observations on a small
sample.
Methods. We performed new observations with the IRAM 30 m and CSO 10.4 m
telescopes, with tracers , HCN, , ,
DCO, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01,
G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05.
Results. We investigated 44 cores including 37 cores reported in previous
work and seven newly-identified cores. Toward the dense cores, we detected 6
DCO, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution
(SED) fits of the 70 to 500 m, we obtained dust
temperature and column density distributions of the IRDCs. We found that emission has a strong correlation with the dust temperature and column
density distributions, while showed the weakest correlation. It
is suggested that is indeed a good tracer in very dense
conditions, but is an unreliable one, as it has a relatively
low critical density and is vulnerable to freezing-out onto the surface of cold
dust grains. The dynamics within IRDCs are active, with infall, outflow, and
collapse; the spectra are abundant especially in deuterium species.
Conclusions. We observe many blueshifted and redshifted profiles,
respectively, with and toward the same core. This
case can be well explained by model "envelope expansion with core collapse
(EECC)".Comment: 24 pages, 11 figures, 4 tables. To be published in A&A. The
resolutions of the pictures are cut dow
Nuclear superfluidity for antimagnetic rotation in Cd and Cd
The effect of nuclear superfluidity on antimagnetic rotation bands in
Cd and Cd are investigated by the cranked shell model with the
pairing correlations and the blocking effects treated by a particle-number
conserving method. The experimental moments of inertia and the reduced
transition values are excellently reproduced. The nuclear superfluidity is
essential to reproduce the experimental moments of inertia. The two-shears-like
mechanism for the antimagnetic rotation is investigated by examining the shears
angle, i.e., the closing of the two proton hole angular momenta, and its
sensitive dependence on the nuclear superfluidity is revealed.Comment: 14 pages, 4 figure
Negative entanglement measure for bipartite separable mixed states
We define a negative entanglement measure for separable states which shows
that how much entanglement one should compensate the unentangled state at least
for changing it into an entangled state. For two-qubit systems and some special
classes of states in higher-dimensional systems, the explicit formula and the
lower bounds for the negative entanglement measure have been presented, and it
always vanishes for bipartite separable pure states. The negative entanglement
measure can be used as a useful quantity to describe the entanglement dynamics
and the quantum phase transition. In the transverse Ising model, the first
derivatives of negative entanglement measure diverge on approaching the
critical value of the quantum phase transition, although these two-site reduced
density matrices have no entanglement at all. In the 1D Bose-Hubbard model, the
NEM as a function of changes from zero to negative on approaching the
critical point of quantum phase transition.Comment: 6 pages, 3 figure
Rotational properties of the superheavy nucleus 256Rf and its neighboring even-even nuclei in particle-number conserving cranked shell model
The ground state band was recently observed in the superheavy nucleus 256Rf.
We study the rotational properties of 256Rf and its neighboring even-even
nuclei by using a cranked shell model (CSM) with the pairing correlations
treated by a particle-number conserving (PNC) method in which the blocking
effects are taken into account exactly. The kinematic and dynamic moments of
inertia of the ground state bands in these nuclei are well reproduced by the
theory. The spin of the lowest observed state in 256Rf is determined by
comparing the experimental kinematic moments of inertia with the PNC-CSM
calculations and agrees with previous spin assignment. The effects of the high
order deformation varepsilon6 on the angular momentum alignments and dynamic
moments of inertia in these nuclei are discussed.Comment: 7 pages, 6 figures; References and discussion about the cranking
Nilsson model added, Fig. 3 modified and Figs. 5 and 6 added; Phys. Rev. C,
in pres
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