26,882 research outputs found
Inversion doublets of reflection-asymmetric clustering in 28Si and their isoscalar monopole and dipole transitions
[Background] Various cluster states of astrophysical interest are expected to
exist in the excited states of . However, they have not been
identified firmly, because of the experimental and theoretical difficulties.
[Purpose] To establish the Mg+, O+C and
Ne+2 cluster bands, we theoretically search for the
negative-parity cluster bands that are paired with the positive-parity bands to
constitute the inversion doublets. We also offer the isoscalar monopole and
dipole transitions as a promising probe for the clustering. We numerically show
that these transition strengths from the ground state to the cluster states are
very enhanced. [Method] The antisymmetrized molecular dynamics with Gogny D1S
effective interaction is employed to calculate the excited states of . The isoscalar monopole and dipole transition strengths are directly
evaluated from wave functions of the ground and excited states. [Results]
Negative-parity bands having Mg+ and O+C cluster
configurations are obtained in addition to the newly calculated
Ne+2 cluster bands. All of them are paired with the
corresponding positive-parity bands to constitute the inversion doublets with
various cluster configurations. The calculation show that the band-head of the
Mg+ and Ne+2 cluster bands are strongly excited
by the isoscalar monopole and dipole transitions. [Conclusions] The present
calculation suggests the existence of the inversion doublets with the
Mg+, O+C and Ne+2
configurations.Because of the enhanced transition strengths, we offer the
isoscalar monopole and dipole transitions as good probe for the
Mg+ and Ne+2 cluster bands.Comment: 28 pages, 8 figure
Infrared spectroscopy under multi-extreme conditions: Direct observation of pseudo gap formation and collapse in CeSb
Infrared reflectivity measurements of CeSb under multi-extreme conditions
(low temperatures, high pressures and high magnetic fields) were performed. A
pseudo gap structure, which originates from the magnetic band folding effect,
responsible for the large enhancement in the electrical resistivity in the
single-layered antiferromagnetic structure (AF-1 phase) was found at a pressure
of 4 GPa and at temperatures of 35 - 50 K. The optical spectrum of the pseudo
gap changes to that of a metallic structure with increasing magnetic field
strength and increasing temperature. This change is the result of the magnetic
phase transition from the AF-1 phase to other phases as a function of the
magnetic field strength and temperature. This result is the first optical
observation of the formation and collapse of a pseudo gap under multi-extreme
conditions.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev.
Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity
We report temperature-dependent polarized optical conductivity
[] spectra of CeFeAl, which is a reference material
for CeRuAl and CeOsAl with an anomalous magnetic
transition at 28 K. The spectrum along the b-axis differs
greatly from that in the -plane, indicating that this material has an
anisotropic electronic structure. At low temperatures, in all axes, a shoulder
structure due to the optical transition across the hybridization gap between
the conduction band and the localized states, namely -
hybridization, appears at 55 meV. However, the gap opening temperature and the
temperature of appearance of the quasiparticle Drude weight are strongly
anisotropic indicating the anisotropic Kondo temperature. The strong
anisotropic nature in both electronic structure and Kondo temperature is
considered to be relevant the anomalous magnetic phase transition in
CeRuAl and CeOsAl.Comment: 5 pages, 4 figure
3alpha clustering in the excited states of 16C
The alpha cluster states of 16C are investigated by using the antisymmetrized
molecular dynamics. It is shown that two different types of alpha cluster
states exist: triangular and linear-chain states. The former has an approximate
isosceles triangular configuration of alpha particles surrounded by four
valence neutrons occupying sd-shell, while the latter has the linearly aligned
alpha particles with two sd-shell neutrons and two pf-shell neutrons. It is
found that the structure of the linear-chain state is qualitatively understood
in terms of the 3/2 pi- and 1/2 sigma- molecular orbit as predicted by
molecular-orbital model, but there exists non-negligible Be+alpha+2n
correlation. The band-head energies of the triangular and linear-chain
rotational bands are 8.0 and 15.5 MeV, and the latter is close to the He+Be
threshold energy. It is also shown that the linear-chain state becomes the
yrast sstate at J=10 with excitation energy 27.8 MeV owing to its very large
moment-of-inertia comparable with hyperdeformation.Comment: 7 pages, 5 figure
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