103 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
Concepts of alpha-particle condensation
Certain aspects of the recently proposed antisymmetrised alpha particle
product state wave function, or THSR alpha cluster wave function, for the
description of the ground state in 8Be, the Hoyle state in 12C, and analogous
states in heavier nuclei, are elaborated in detail. For instance, the influence
of antisymmetrisation in the Hoyle state on the bosonic character of the alpha
particles is studied carefully. It is shown to be weak, so that bosonic aspects
are predominant. The de Broglie wave length of alpha particles in the Hoyle
state is shown to be much larger than the inter-alpha distance. It is pointed
out that the bosonic features of low density alpha gas states have measurable
consequences, one of which, that is enhanced multi-alpha decay properties,
likely already have been detected. Consistent with experiment, the width of the
proposed analogue to the Hoyle state in 16O at the excitation energy of
E_x=15.1 MeV is estimated to be very small (34 keV), lending credit to the
existence of heavier Hoyle-like states. The intrinsic single boson density
matrix of a self-bound Bose system can, under physically desirable boundary
conditions, be defined unambiguously. One eigenvalue then separates out, being
close to the number of alpha's in the system. Differences between Brink and
THSR alpha cluster wave functions are worked out. No cluster model of the Brink
type can describe the Hoyle state with a single configuration. On the contrary,
many superpositions of the Brink type are necessary, implying delocalisation
towards an alpha product state. It is shown that single alpha particle orbits
in condensates of different nuclei are almost the same. It is thus argued that
alpha particle antisymmetrised product states of the THSR type are a very
promising novel and useful concept in nuclear physics.Comment: 16 pages, 14 figures, to appear in PR
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 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.
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
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