2,604 research outputs found
Evolving theoretical descriptions of heavy-ion fusion :from phenomenological to microscopic approaches
We overview the current status of theoretical approaches for heavy-ion fusion
reactions at subbarrier energies. We particularly discuss theoretical
challenges in the coupled-channels approach, that include i) a description of
deep subbarrier hindrance of fusion cross sections, ii) the role of nuclear
dissipation, iii) fusion of unstable nuclei, and iv) an interplay between
fusion and multi-nucleon transfer processes. We also present results of a
semi-microscopic approach to heavy-ion fusion reactions, that combines the
coupled-channels approach with state-of-the-art microscopic nuclear structure
calculations.Comment: 6 pages, 5 eps figures. A talk given at the International conference
on heavy-ion collisions at near-barrier energies (FUSION17), February 20-24,
2017, Hobart, Australi
Dynamical particle-phonon couplings in proton emission from spherical nuclei
We present results of coupled-channels calculations which are performed to
understand the role of vibrational excitations of the daughter nucleus in
proton emission decay of spherical nuclei. It is shown that the experimental
decay rates from the 2, 3 and 1 states in proton
emitting nuclei Re are reproduced simultaneously when the
quadrupole phonon excitation of the core nuclei is taken into account. We apply
the formalism also to the Tm nucleus and show that good agreement is
achieved with the recently measured branching ratio for the fine structure.Comment: 10 pages, 3 eps figures, uses psfig.sty and ptptex.sty. A talk given
at the Yukawa International Seminar 2001 on "Physics of Unstable Nuclei",
Nov. 2001, Kyoto, Japa
Importance of Non-Linear Couplings in Fusion Barrier Distributions and Mean Angular Momenta
The effects of higher order coupling of surface vibrations to the relative
motion on heavy-ion fusion reactions at near-barrier energies are investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. It is shown that the shape of fusion
barrier distributions and the energy dependence of the average angular momentum
of the compound nucleus can significantly change when the higher order
couplings are included. The role of octupole vibrational excitation of ^{16}O
in the ^{16}O + ^{144}Sm fusion reaction is also discussed using the all order
coupled-channels equations.Comment: 8 pages, 6 figures, To be published in the Proceedings of the FUSION
97 Conference, South Durras, Australia, March 1997 (J. Phys. G
Potential inversion with subbarrier fusion data revisited
We invert experimental data for heavy-ion fusion reactions at energies well
below the Coulomb barrier in order to directly determine the internucleus
potential between the colliding nuclei. In contrast to the previous
applications of the inversion formula, we explicitly take into account the
effect of channel couplings on fusion reactions, by assuming that fusion cross
sections at deep subbarrier energies are governed by the lowest barrier in the
barrier distribution. We apply this procedure to the O +Sm and
O +Pb reactions, and find that the inverted internucleus
potential are much thicker than phenomenological potentials. A relation to the
steep fall-off phenomenon of fusion cross sections recently found at deep
subbarrier energies is also discussed.Comment: 5 pages, 3 eps figure
Applicability of the orientation average formula in heavy-ion fusion reactions of deformed nuclei
In heavy-ion fusion reactions involving a well deformed nucleus, one often
assumes that the orientation of the target nucleus does not change during the
reaction. We discuss the accuracy of this procedure by analyzing the excitation
function of the fusion cross section and the fusion barrier distribution in the
reactions of Sm target with various projectiles ranging from C
to Ar. It is shown that the approximation gradually looses its accuracy
with increasing charge product of the projectile and target nuclei because of
the effects of finite excitation energy of the target nucleus. The relevance of
such inaccuracy in analyzing the experimental data is also discussed.Comment: 5 pages and 3 figure
Continuum QRPA in the coordinate space representation
We formulate a quasi-particle random phase approximation (QRPA) in the
coordinate space representation. This model is a natural extension of the RPA
model of Shlomo and Bertsch to open-shell nuclei in order to take into account
pairing correlations together with the coupling to the continuum. We apply it
to the Sn nucleus and show that low-lying excitation modes are
significantly influenced by the pairing effects although the effects are
marginal in the giant resonance region. The dependence of the pairing effect on
the parity of low-lying collective mode is also discussed.Comment: RevTex, 21 pages, 10 eps figure
Odd-even staggering of reaction cross sections for 22,23,24O isotopes
The interaction cross sections of O nuclei at 900 MeV/nucleon have
been measured recently by Kanungo {\it et al.}. We show that the odd-even
staggering parameter of interaction cross sections deduced from these new data
agrees well with the theoretical systematics expected for the neutron
separation energy of =2.740.120 MeV for O. We also discuss
briefly the energy dependence of the staggering parameter.Comment: 2 pages, 1 figur
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