96 research outputs found
Three-body model for an isoscalar spin-triplet neutron-proton pair in
We discuss the isoscalar pairing correlation in the low-lying
states of nucleus. To this end, we employ
three-body model with the model space constructed by
self-consistent mean-field calculations. The model is developed with both
non-relativistic and relativistic effective interactions, the latter of which
are found to be more realistic for the present case due to the pseudo-spin
symmetry. It turns out that the pairing scheme is strongly
hindered in Sb with the relativistic model because of the near
degeneracy of the and orbitals in the valence space. This
pair-breaking effect is clearly seen in the charge-exchange Gamow-Teller-type
transitions rather than in the binding energies of and states.Comment: 12 pages, 10 figures. The title has been changed. Accepted for
publication in Phys. Rev.
Collectivity in small and large amplitude microscopic mean-field dynamic
The time-dependent energy density functional with pairing allows to describe
a large variety of phenomena from small to large amplitude collective motion.
Here, we briefly summarize the recent progresses made in the field using the
TD-BCS approach. A focus is made on the mapping of the microscopic mean-field
dynamic to the macroscopic dynamic in collective space. A method is developed
to extract the collective mass parameter from TD-EDF. Illustration is made on
the fission of Fm. The collective mass and collective momentum
associated to quadrupole deformation including non-adiabatic effects is
estimated along the TD-EDF path. With these information, the onset of
dissipation during fission is discussed.Comment: Proceeding of the XXII Nuclear Physics Workshop, Kazimierz, 2015,
Polan
Collective aspects deduced from time-dependent microscopic mean-field with pairing: application to the fission process
Given a set of collective variables, a method is proposed to obtain the
associated conjugated collective momenta and masses starting from a microscopic
time-dependent mean-field theory. The construction of pairs of conjugated
variables is the first step to bridge microscopic and macroscopic approaches.
The method is versatile and can be applied to study a large class of nuclear
processes. An illustration is given here with the fission of Fm. Using
the quadrupole moment and eventually higher-order multipole moments, the
associated collective masses are estimated along the microscopic mean-field
evolution. When more than one collective variable are considered, it is shown
that the off-diagonal matrix elements of the inertia play a crucial role. Using
the information on the quadrupole moment and associated momentum, the
collective evolution is studied. It is shown that dynamical effects beyond the
adiabatic limit are important. Nuclei formed after fission tend to stick
together for longer time leading to a dynamical scission point at larger
distance between nuclei compared to the one anticipated from the adiabatic
energy landscape. The effective nucleus-nucleus potential felt by the emitted
nuclei is finally extracted.Comment: 12 pages, 9 figure
A simplified BBGKY hierarchy for correlated fermionic systems from a Stochastic Mean-Field approach
The stochastic mean-field (SMF) approach allows to treat correlations beyond
mean-field using a set of independent mean-field trajectories with appropriate
choice of fluctuating initial conditions. We show here, that this approach is
equivalent to a simplified version of the Bogolyubov-Born-Green-Kirkwood-Yvon
(BBGKY) hierarchy between one-, two-, ..., N-body degrees of freedom. In this
simplified version, one-body degrees of freedom are coupled to fluctuations to
all orders while retaining only specific terms of the general BBGKY hierarchy.
The use of the simplified BBGKY is illustrated with the Lipkin-Meshkov-Glick
(LMG) model. We show that a truncated version of this hierarchy can be useful,
as an alternative to the SMF, especially in the weak coupling regime to get
physical insight in the effect beyond mean-field. In particular, it leads to
approximate analytical expressions for the quantum fluctuations both in the
weak and strong coupling regime. In the strong coupling regime, it can only be
used for short time evolution. In that case, it gives information on the
evolution time-scale close to a saddle point associated to a quantum
phase-transition. For long time evolution and strong coupling, we observed that
the simplified BBGKY hierarchy cannot be truncated and only the full SMF with
initial sampling leads to reasonable results.Comment: 10 pages, 4 figure
Microscopic description of large amplitude collective motion in the nuclear astrophysics context
In the last 10 years, we have observed an important increase of interest in
the application of time-dependent energy density functional theory (TD-EDF).
This approach allows to treat nuclear structure and nuclear reaction from small
to large amplitude dynamics in a unified framework. The possibility to perform
unrestricted three-dimensional simulations using state of the art effective
interactions has opened new perspectives. In the present article, an overview
of applications where the predictive power of TD-EDF has been benchmarked is
given. A special emphasize is made on processes that are of astrophysical
interest. Illustrations discussed here include giant resonances, fission,
binary and ternary collisions leading to fusion, transfer and deep inelastic
processes.Comment: To appear in a special issue of IJMPE on "Collectivity in Nuclei,
Neutrinos, and Neutron Stars
Vapochromic films of pi-conjugated polymers based on coordination and desorption at hypervalent tin(iv)-fused azobenzene compounds
We report the synthesis and vapochromic behaviors of film materials consisting of hypervalent tin-containing π-conjugated polymers. We prepared copolymers with brominated tin-fused azobenzenes and modified fluorene having tetraethylene glycol as a side chain. The synthesized polymers showed good film-formability and high affinity with coordinating solvent molecules such as dimethyl sulfoxide (DMSO). In particular, we discovered distinct color changes from blue to purple when exposed to DMSO vapor. It was revealed that color changes should originate from reversible alteration of the coordination-number between five and six of hypervalent tin(IV) in the azobenzene compounds involved in the main-chain conjugation. Moreover, we also observed that binding constants between tin and coordinating solvents could be influenced by two substitutions on the tin atom and subsequently modulated responsivity of vapochromism in films by altering the type of substituent. Furthermore, the color-change behaviors can be estimated by quantum calculations with density functional theory. We demonstrate not only that hypervalent tin can work as a switching unit for modulating the electronic structures of π-conjugated polymers triggered by solvent coordination but also that vapochromic behaviors in films can be predicted by estimating the affinity between hypervalent tin and solvent molecules with theoretical calculations
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