5,906 research outputs found

### Interpretation of Coulomb breakup of 31Ne in terms of deformation

The recent experimental data on Coulomb breakup of the nucleus $^{31}$Ne are
interpreted in terms of deformation. The measured large one-neutron removal
cross-section indicates that the ground state of $^{31}$Ne is either s- or
p-halo. The data can be most easily interpreted as the spin of the ground state
being 3/2$^-$ coming from either the Nilsson level [330 1/2] or [321 3/2]
depending on the neutron separation energy $S_n$. However, the possibility of
1/2$^{+}$ coming from [200 1/2] is not excluded. It is suggested that if the
large ambiguity in the measured value of $S_n$ of $^{31}$Ne, 0.29$\pm1.64$ MeV,
can be reduced by an order of magnitude, say to be $\pm$100 keV, one may get a
clear picture of the spin-parity of the halo ground state.Comment: 8 pages, 4 figure

### Nilsson diagrams for light neutron-rich nuclei with weakly-bound neutrons

Using Woods-Saxon potentials and the eigenphase formalism for one-particle
resonances, one-particle bound and resonant levels for neutrons as a function
of quadrupole deformation are presented, which are supposed to be useful for
the interpretation of spectroscopic properties of some light neutron-rich
nuclei with weakly-bound neutrons. Compared with Nilsson diagrams in text books
which are constructed using modified oscillator potentials, we point out a
systematic change of the shell structure in connection with both weakly-bound
and resonant one-particle levels related to small orbital angular momenta
$\ell$. Then, it is seen that weakly-bound neutrons in nuclei such as
$^{15-19}$C and $^{33-37}$Mg may prefer to being deformed as a result of
Jahn-Teller effect, due to the near degeneracy of the 1d$_{5/2}$-2s$_{1/2}$
levels and the 1f$_{7/2}$-2p$_{3/2}$ levels in the spherical potential,
respectively. Furthermore, the absence of some one-particle resonant levels
compared with the Nilsson diagrams in text books is illustrated.Comment: 12 pages, 5 figure

### Coulomb corrections to superallowed beta decay in nuclei

Corrections to the superallowed beta decay matrix elements are evaluated in
perturbation theory using the notion of the isovector monopole resonance. The
calculation avoids the separation into different contributions and thus
presents a consistent, systematic and more transparent approach. Explicit
expressions for the Coulomb correction as a function of mass number A, are
given.Comment: 10 page

### The intruder feature of 31Mg and the coexistence of many particle and many hole states

The low-lying level structure of $^{31}{\rm Mg}$ has been investigated by the
antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM)
with the Gogny D1S force. It is shown that the N=20 magic number is broken and
the ground state has the pure neutron $2p3h$ configuration. The coexistence of
many particle and many hole states at very low excitation energy is discussed

### Complementarity and Scientific Rationality

Bohr's interpretation of quantum mechanics has been criticized as incoherent
and opportunistic, and based on doubtful philosophical premises. If so Bohr's
influence, in the pre-war period of 1927-1939, is the harder to explain, and
the acceptance of his approach to quantum mechanics over de Broglie's had no
reasonable foundation. But Bohr's interpretation changed little from the time
of its first appearance, and stood independent of any philosophical
presuppositions. The principle of complementarity is itself best read as a
conjecture of unusually wide scope, on the nature and future course of
explanations in the sciences (and not only the physical sciences). If it must
be judged a failure today, it is not because of any internal inconsistency.Comment: 29 page

### On the relation between $E(5)-$models and the interacting boson model

The connections between the $E(5)-$models (the original E(5) using an
infinite square well, $E(5)-\beta^4$, $E(5)-\beta^6$ and $E(5)-\beta^8$), based
on particular solutions of the geometrical Bohr Hamiltonian with
$\gamma$-unstable potentials, and the interacting boson model (IBM) are
explored. For that purpose, the general IBM Hamiltonian for the $U(5)-O(6)$
transition line is used and a numerical fit to the different $E(5)-$models
energies is performed, later on the obtained wavefunctions are used to
calculate B(E2) transition rates. It is shown that within the IBM one can
reproduce very well all these $E(5)-$models. The agreement is the best for
$E(5)-\beta^4$ and reduces when passing through $E(5)-\beta^6$, $E(5)-\beta^8$
and E(5), where the worst agreement is obtained (although still very good for a
restricted set of lowest lying states). The fitted IBM Hamiltonians correspond
to energy surfaces close to those expected for the critical point. A phenomenon
similar to the quasidynamical symmetry is observed

### Model of molecular bonding based on the Bohr-Sommerfeld picture of atoms

We develop a model of molecular binding based on the Bohr-Sommerfeld
description of atoms together with a constraint taken from conventional quantum
mechanics. The model can describe the binding energy curves of H2, H3 and other
molecules with striking accuracy. Our approach treats electrons as point
particles with positions determined by extrema of an algebraic energy function.
Our constrained model provides a physically appealing, accurate description of
multi-electron chemical bonds.Comment: 5 pages, 7 figures, to appear in Physics Letters

### Stellar weak decay rates in neutron-deficient medium-mass nuclei

Weak decay rates under stellar density and temperature conditions holding at
the rapid proton capture process are studied in neutron-deficient medium-mass
waiting point nuclei extending from Ni up to Sn. Neighboring isotopes to these
waiting point nuclei are also included in the analysis. The nuclear structure
part of the problem is described within a deformed Skyrme Hartree-Fock + BCS +
QRPA approach, which reproduces not only the beta-decay half-lives but also the
available Gamow-Teller strength distributions, measured under terrestrial
conditions. The various sensitivities of the decay rates to both density and
temperature are discussed. In particular, we study the impact of contributions
coming from thermally populated excited states in the parent nucleus, as well
as the competition between beta decays and continuum electron captures.Comment: 24 pages, 16 figure

### Relationship between X(5)-models and the interacting boson model

The connections between the X(5)-models (the original X(5) using an infinite
square well, X(5)-$\beta^8$, X(5)-$\beta^6$, X(5)-$\beta^4$, and
X(5)-$\beta^2$), based on particular solutions of the geometrical Bohr
Hamiltonian with harmonic potential in the $\gamma$ degree of freedom, and the
interacting boson model (IBM) are explored. This work is the natural extension
of the work presented in [1] for the E(5)-models. For that purpose, a quite
general one- and two-body IBM Hamiltonian is used and a numerical fit to the
different X(5)-models energies is performed, later on the obtained wave
functions are used to calculate B(E2) transition rates. It is shown that within
the IBM one can reproduce well the results for energies and B(E2) transition
rates obtained with all these X(5)-models, although the agreement is not so
impressive as for the E(5)-models. From the fitted IBM parameters the
corresponding energy surface can be extracted and it is obtained that,
surprisingly, only the X(5) case corresponds in the moderate large N limit to
an energy surface very close to the one expected for a critical point, while
the rest of models seat a little farther.Comment: Accepted in Physical Review

### Self-consistent Skyrme QRPA for use in axially-symmetric nuclei of arbitrary mass

We describe a new implementation of the quasiparticle random phase
approximation (QRPA) in axially-symmetric deformed nuclei with Skyrme and
volume-pairing energy-density functionals. After using a variety of tests to
demonstrate the accuracy of the code in ^{24,26}Mg and ^{16}O, we report the
first fully self-consistent application of the Skyrme QRPA to a heavy deformed
nucleus, calculating strength distributions for several K^pi in ^{172}Yb. We
present energy-weighted sums, properties of gamma-vibrational and low-energy
K^pi=0^+ states, and the complete isovector E1 strength function. The QRPA
calculation reproduces the properties of the low-lying 2^+ states as well or
better than it typically does in spherical nuclei.Comment: 5 pages, 6 figure

- âŠ