5,255 research outputs found
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
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
Subbarrier fusion reactions with dissipative couplings
Using the random matrix model, we discuss the effect of couplings to
non-collective states on the penetrability of a one dimensional potential
barrier. We show that these non-collective excitations hinder the penetrability
and thus smear the barrier distribution at energies above the barrier, while
they do not affect significantly the penetrability at deep subbarrier energies.
The energy dependence of the Q-value distribution obtained with this model is
also discussed.Comment: 4 pages, 2 figures. A talk given at the 10th international conference
on nucleus-nucleus collisions (NN2009), Aug. 16-21, 2009, Beijing, Chin
Evolution of concentration in the United Kingdom cement industry: Structure, conduct, and performance. Evolution of concentration and competition series No. 20, November 1978
Non-collective excitations in low-energy heavy-ion reactions: applicability of the random-matrix model
We investigate the applicability of a random-matrix model to the description
of non-collective excitations in heavy-ion reactions around the Coulomb
barrier. To this end, we study fusion in the reaction O + Pb,
taking account of the known non-collective excitations in the Pb
nucleus. We show that the random-matrix model for the corresponding couplings
reproduces reasonably well the exact calculations, obtained using empirical
deformation parameters. This implies that the model may provide a powerful
method for systems in which the non-collective couplings are not so well known.Comment: 6 pages, 4 figure
Research into practice : collaboration for leadership in applied health research and care (CLAHRC) for Nottinghamshire, Derbyshire, Lincolnshire (NDL)
To address the problem of translation from research-based evidence to routine healthcare practice, the Collaboration for Leadership in Applied Health Research and Care for Nottinghamshire, Derbyshire, and Lincolnshire (CLAHRC-NDL) was funded by the National Institute for Health Research as one of nine CLAHRCs across England. This paper outlines the underlying theory and its application that CLAHRC-NDL has adopted, as a case example that might be generalised to practice outside the CLAHRC, in comparison to alternative models of implementation
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