46,370 research outputs found
Classical Analysis of Phenomenological Potentials for Metallic Clusters
The classical trajectories of single particle motion in a Wodds-Saxon and a
modified Nilsson potential are studied for axial quadrupole deformation. Both
cases give rise to chaotic behaviour when the deformation in the Woods-Saxon
and the l**2 term in the modified Nilsson potential are turned on. Important
similarities, in particular with regard to the shortest periodic orbits, have
been found.Comment: 9 pages LaTex + 4 figures available via e-mail requests from the
authors, to appear in Phys.Rev.Let
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
. Then, it is seen that weakly-bound neutrons in nuclei such as
C and Mg may prefer to being deformed as a result of
Jahn-Teller effect, due to the near degeneracy of the 1d-2s
levels and the 1f-2p 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
Triaxiality in 48Cr
Rotational behavior inducing triaxiality is discussed for 48Cr in the cranked
Nilsson-Strutinsky (CNS) model, as well as in the spherical shell model. It is
shown that the low-spin region up to about I=8, has a prolate well-deformed
shape. At higher spins the shape is triaxial with a "negative-gamma"
deformation, that is, with rotation around the classically forbidden
intermediate axis. By comparing calculated B(E2)-values and spectroscopic
quadrupole moments in the CNS with spherical shell model results and
experimental data, the triaxial rotation around the intermediate axis is
confirmed.Comment: 9 pages, including 6 figures; submitted to Physics Letters
Reaction cross sections of the deformed halo nucleus 31Ne
Using the Glauber theory, we calculate reaction cross sections for the
deformed halo nucleus Ne. To this end, we assume that the Ne
nucleus takes the Ne + structure. In order to take into account the
rotational excitation of the core nucleus Ne, we employ the
particle-rotor model (PRM). We compare the results to those in the adiabatic
limit of PRM, that is, the Nilsson model, and show that the Nilsson model works
reasonably well for the reaction cross sections of Ne. We also
investigate the dependence of the reaction cross sections on the ground state
properties of Ne, such as the deformation parameter and the p-wave
component in the ground state wave function.Comment: 7 pages, 6 eps figure
Nilsson solutions for irregular A-hypergeometric systems
We study the solutions of irregular A-hypergeometric systems that are
constructed from Gr\"obner degenerations with respect to generic positive
weight vectors. These are formal logarithmic Puiseux series that belong to
explicitly described Nilsson rings, and are therefore called (formal) Nilsson
series. When the weight vector is a perturbation of (1,...,1), these series
converge and provide a basis for the (multivalued) holomorphic hypergeometric
functions in a specific open subset of complex n-space. Our results are more
explicit when the parameters are generic or when the solutions studied are
logarithm-free. We also give an alternative proof of a result of Schulze and
Walther that inhomogeneous A-hypergeometric systems have irregular
singularities.Comment: Terminology changed: see Definition 2.6 in current version.
Corrections made to Theorem 6.6, Corollary 6.7 and Corollary 6.8 in version 1
(now Theorem 6.7, Corollary 6.9 and Corollary 6.10, respectively). Added
Corollary 6.3 and Example 6.8. Some stylistic changes, some typos correcte
Negative c-axis magnetoresistance in graphite
We have studied the c-axis interlayer magnetoresistance (ILMR), R_c(B) in
graphite. The measurements have been performed on strongly anisotropic highly
oriented pyrolytic graphite (HOPG) samples in magnetic field up to B = 9 T
applied both parallel and perpendicular to the sample c-axis in the temperature
interval 2 K < T < 300 K. We have observed negative magnetoresistance, dR_c/dB
< 0, for B || c-axis above a certain field B_m(T) that reaches its minimum
value B_m = 5.4 T at T = 150 K. The results can be consistently understood
assuming that ILMR is related to a tunneling between zero-energy Landau levels
of quasi-two-dimensional Dirac fermions, in a close analogy with the behavior
reported for alpha-(BEDT-TTF)2I3 [N. Tajima et al., Phys. Rev. Lett. 102,
176403 (2009)], another multilayer Dirac electron system.Comment: 14 pages, including 4 figure
Parametrizations of triaxial deformation and E2 transitions of the wobbling band
By the very definition the triaxial deformation parameter is related
to the expectation values of the K=0 and K=2 components of the intrinsic
quadrupole tensor operator. On the other hand, using the same symbol
"", various different parametrizations of triaxial deformation have
been employed, which are suitable for various types of the mean-field
potentials. It is pointed out that the values of various "" are quite
different for the same actual triaxial deformation, especially for the large
deformation; for example, the difference can be almost a factor two for the
case of the triaxial superdeformed bands recently observed in the Hf and Lu
nuclei. In our previous work, we have studied the wobbling band in Lu nuclei by
using the microscopic framework of the cranked Nilsson mean-field and the
random phase approximation, where the most serious problem is that the
calculated B(E2) value is about factor two smaller. It is shown that the origin
of this underestimation can be mainly attributed to the small triaxial
deformation; if is used the same triaxial deformation as in the analysis of the
particle-rotor model, the calculated B(E2) increases and gives correct
magnitude compared with the experimental data.Comment: 10 pages, 9 figure
Roles of triaxiality and residual interaction in signature inversions of A~130 odd-odd nuclei
Rotational bands with (neutron h_11/2)^1 (proton h_11/2)^1 configurations are
studied using a particle-rotor model in which a proton and a neutron
quasiparticles interacting through a zero-range force are coupled with a
triaxial rotor. It is shown for 124Cs that one can reproduce the signature
dependence of energy and B(M1)/B(E2) ratio best when one takes into account
gamma-deformations with irrotational-flow moment of inertia in addition to the
proton-neutron interaction proposed by Semmes and Ragnarsson. Including both
effects, a systematic calculation of signature splittings is performed for Cs,
La isotopes and N=75 isotones to be compared with experiments. Discussions are
also done on the deficiencies of the cranking model concerning its
applicability to signature inversion phenomena in odd-odd nuclei.Comment: 19 pages of LaTex, (11 figures not included, hard copy available upon
request), UT-Komaba 93-1
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