575 research outputs found
Effects of mass renormalization on the surface properties of heavy-ion fusion potential
We discuss the effects of fast nuclear excitations on heavy-ion fusion
reactions at energies near and below the Coulomb barrier. Using the fusion of
two Ca nuclei as an example and the inversion method, we show that the
mass renormalization induced by fast nuclear excitations leads to a large
surface diffuseness in the effective potential for heavy-ion fusion reactions.Comment: 13 pages, Late
Mapping from quasi-elastic scattering to fusion reactions
The fusion barrier distribution has provided a nice representation for the
channel coupling effects on heavy-ion fusion reactions at energies around the
Coulomb barrier. Here we discuss how one can extract the same representation
using the so called sum-of-differences (SOD) method with quasi-elastic
scattering cross sections. In contrast to the conventional quasi-elastic
barrier distribution, the SOD barrier distribution has an advantage in that it
can be applied both to non-symmetric and symmetric systems. It is also the case
that the correspondence to the fusion barrier distribution is much better than
the quasi-elastic barrier distribution. We demonstrate its usefulness by
studying O+Sm, Ni+Ni, and C+C
systems.Comment: 6 pages, 9 figures. A talk given at VI International Conference
FUSION14, Feb. 24-28, 2014, New Delhi, Indi
Quasi-elastic barrier distribution as a tool for investigating unstable nuclei
The method of fusion barrier distribution has been widely used to interpret
the effect of nuclear structure on heavy-ion fusion reactions around the
Coulomb barrier. We discuss a similar, but less well known, barrier
distribution extracted from large-angle quasi-elastic scattering. We argue that
this method has several advantages over the fusion barrier distribution, and
offers an interesting tool for investigating unstable nuclei.Comment: 4 pages, 4 eps figures. A talk given at the XXVII Reuniao de Trabalho
em Fisica Nuclear no Brazil, September 7 - 11, 2004, Santos, Brazil. To be
published in the Brazilian Journal of Physic
On the Wong cross section and fusion oscillations
We re-examine the well-known Wong formula for heavy-ion fusion cross
sections. Although this celebrated formula yields almost exact results for
single-channel calculations for relatively heavy systems such as
O+Sm, it tends to overestimate the cross section for light
systems such as C+C. We generalise the formula to take account of
the energy dependence of the barrier parameters and show that the
energy-dependent version gives results practically indistinguishable from a
full quantal calculation. We then examine the deviations arising from the
discrete nature of the intervening angular momenta, whose effect can lead to an
oscillatory contribution to the excitation function. We recall some compact,
analytic expressions for these oscillations, and highlight the important
physical parameters that give rise to them. Oscillations in symmetric systems
are discussed, as are systems where the target and projectile identities can be
exchanged via a strong transfer channel.Comment: 14 pages, 14 figure
Subbarrier fusion of carbon isotopes: from resonance structure to fusion oscillations
At energies below the Coulomb barrier, the fusion excitation function for the
C+C system shows prominent fine structures, whereas that for the
C+C system behaves more smoothly as a function of energy. We
demonstrate that these different behaviors can be simultaneously reproduced
using an optical potential in which the strength of the imaginary part is
proportional to the level density of each compound nucleus. We also discuss the
oscillatory behavior of fusion excitation function for these systems observed
at energies above the Coulomb barrier from a view point of quantum mechanical
systems with identical particles.Comment: 6 pages, 6 eps figures. A talk given at NUBA conference series-1:
Nuclear Physics and Astrophysics, September 15-21, Antalya, Turke
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
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
Role of non-collective excitations in low-energy heavy-ion reactions
We investigate the effect of single-particle excitations on heavy-ion
reactions at energies near the Coulomb barrier. To this end, we describe
single-particle degrees of freedom with the random matrix theory and solve the
coupled-channels equations for one-dimensional systems. We find that the
single-particle excitations hinder the penetrability at energies above the
barrier, leading to a smeared barrier distribution. This indicates that the
single-particle excitations provide a promising way to explain the difference
in a quasi-elastic barrier distribution recently observed in Ne +
Zr systems.Comment: 8 pages, 7 figure
- âŠ