89 research outputs found
New Treatment of Resonances with Bound State Approximation by Using Pseudo Potential
We propose a new approach to extract the wave functions of resonances by the
bound state approximation which gives the mixed states of the resonance
components and the continuum ones. In our approach, on the basis of the method
of analytic continuation in the coupling constant (ACCC), we construct Pad\'e
rational function by adopting the positive energies as well as the negative
ones. We report the result of the application of this new method to the second
state of C which was studied with the ACCC method in our previous
work. It is found that the resonance parameters obtained by the ACCC method are
well reproduced by the new method. Some advantages over the ACCC method are
also shown.Comment: 10pages, 2figures, submitted to Prog. Theor. Phys, changed content,
added reference
Alpha-particle condensation in nuclei
A round up of the present status of the conjecture that n alpha nuclei form
an alpha-particle condensate in excited states close to the n alpha threshold
is given. Experiments which could demonstrate the condensate character are
proposed. Possible lines of further theoretical developments are discussed.Comment: 6 page
Bound clusters on top of doubly magic nuclei
An effective particle equation is derived for cases where an
particle is formed on top of a doubly magic nucleus. As an example, we
consider Po with the on top of the Pb core. We will
consider the core nucleus infinitely heavy, so that the particle moves
with respect to a fixed center, i.e., recoil effects are neglected. The fully
quantal solution of the problem is discussed. The approach is inspired by the
THSR (Tohsaki-Horiuchi-Schuck-R\"{o}pke) wave function concept that has been
successfully applied to light nuclei. Shell model calculations are improved by
including four-particle (-like) correlations that are of relevance when
the matter density becomes low. In the region where the -like cluster
penetrates the core nucleus, the intrinsic bound state wave function transforms
at a critical density into an unbound four-nucleon shell model state.
Exploratory calculations for Po are presented. Such preformed cluster
states are only hardly described by shell model calculations. Reasons for
different physics behavior of an -like cluster with respect to a
deuteron-like cluster are discussed.Comment: 24 pages, 5 figure
Alpha cluster condensation in 12C and 16O
A new -cluster wave function is proposed which is of the
-particle condensate type. Applications to C and O show
that states of low density close to the 3 resp. 4 -particle threshold
in both nuclei are possibly of this kind. It is conjectured that all
self-conjugate 4 nuclei may show similar features.Comment: 4 pages, 2 tables, 2 figure
Alpha Decay Width of Po from a quartetting wave function approach
A microscopic calculation of -cluster preformation probability and
decay width in the typical emitter Po is presented.
Results are obtained by improving a recent approach to describe
preformation in Po [Phys. Rev. C 90, 034304 (2014)] implementing
four-nucleon correlations (quartetting). Using the actually measured density
distribution of the Pb core, the calculated alpha decay width of
Po agrees fairly well with the measured one.Comment: 7 pages, 5 figures, 1 table, submitted to Phys. Rev.
Monopole Excitation to Cluster States
We discuss strength of monopole excitation of the ground state to cluster
states in light nuclei. We clarify that the monopole excitation to cluster
states is in general strong as to be comparable with the single particle
strength and shares an appreciable portion of the sum rule value in spite of
large difference of the structure between the cluster state and the
shell-model-like ground state. We argue that the essential reasons of the large
strength are twofold. One is the fact that the clustering degree of freedom is
possessed even by simple shell model wave functions. The detailed feature of
this fact is described by the so-called Bayman-Bohr theorem which tells us that
SU(3) shell model wave function is equivalent to cluster model wave function.
The other is the ground state correlation induced by the activation of the
cluster degrees of freedom described by the Bayman-Bohr theorem. We
demonstrate, by deriving analytical expressions of monopole matrix elements,
that the order of magnitude of the monopole strength is governed by the first
reason, while the second reason plays a sufficient role in reproducing the data
up to the factor of magnitude of the monopole strength. Our explanation is made
by analysing three examples which are the monopole excitations to the
and states in O and the one to the state in C.
The present results imply that the measurement of strong monopole transitions
or excitations is in general very useful for the study of cluster states.Comment: 11 pages, 1 figure: revised versio
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