369 research outputs found
- Double Folding Cluster Potential Description of the C+Mg System
We present a simultaneous analysis of the elastic scattering and fusion
cross-section data of the C+Mg system around the Coulomb barrier
and over energies by using the microscopic - double folding
cluster potential within the framework of the optical model and the
coupled-channels formalism. The - double folding cluster
potential is obtained by using the -cluster distribution densities of
the nuclei in the usual double folding procedure. The microscopic potential
results are compared with the findings of the phenomenological deep and shallow
potentials. It is subsequently shown that only phenomenological deep real,
microscopic nucleon-nucleon and - double folding cluster
potentials provide a consistent description of the angular distributions and
fusion cross-section data simultaneously. The effect of the inclusion of the
excited states of the target nucleus Mg on the fusion cross-section
predictions is also determined by the coupled-channels calculations, which are
shown to improve the agreement.Comment: 4 pages Latex RevTex4 with 2 EPS Figures. Accepted for publications
in Phys. Rev.
Asymptotic Iteration Method Solutions to the Relativistic Duffin-Kemmer-Petiau Equation
A simple exact analytical solution of the relativistic Duffin-Kemmer-Petiau
equation within the framework of the asymptotic iteration method is presented.
Exact bound state energy eigenvalues and corresponding eigenfunctions are
determined for the relativistic harmonic oscillator as well as the Coulomb
potentials. As a non-trivial example, the anharmonic oscillator is solved and
the energy eigenvalues are obtained within the perturbation theory using the
asymptotic iteration method.Comment: 17 pages written with LaTeX Revtex4. accepted for publication in
Journal of Mathematical Physic
Failure of the Standard Coupled-Channels Method in Describing the Inelastic Reaction Data: On the Use of a New Shape for the Coupling Potential
We present the failure of the standard coupled-channels method in explaining
the inelastic scattering together with other observables such as elastic
scattering, excitation function and fusion data. We use both microscopic
double-folding and phenomenological deep potentials with shallow imaginary
components. We argue that the solution of the problems for the inelastic
scattering data is not related to the central nuclear potential, but to the
coupling potential between excited states. We present that these problems can
be addressed in a systematic way by using a different shape for the coupling
potential instead of the usual one based on Taylor expansion.Comment: 10 pages, 4 figures, 1 table, Latex:RevTex4 published in J. Phys. G:
Nucl. Part. Phy
Coulomb distortion and medium corrections in nucleon-removal reactions
One-nucleon removal reactions at or above the Fermi energy are important
tools to explore the single-particle structure of exotic nuclei. Experimental
data must be compared with calculations to extract structure information,
evaluate correlation effects in nuclei or determine reaction rates for nuclear
astrophysics. However, there is insufficient knowledge to calculate accurately
the cross sections for these reactions. We evaluate the contributions of the
final state interaction (FSI) and of the medium modifications of the
nucleon-nucleon interactions and obtain the shapes and magnitudes of momentum
distributions. Such effects have been often neglected in the literature.
Calculations for reactions at energies 35 - 1000 MeV/nucleon are reported and
compared to published data. For consistency, the state-of-the-art eikonal
method for stripping and diffraction dissociation is used. We find that the two
effects are important and their relative contributions vary with the energy and
with the atomic and mass number of the projectile involved. These two often
neglected effects modify considerably the one-nucleon removal cross sections.
As expected, the effect are largest at lower energies, around 50 MeV/nucleon
and on heavy targets.Comment: 12 pages, 10 figures. Accpeted for publication in the Physical Review
C. arXiv admin note: text overlap with arXiv:nucl-th/0407026 by other author
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An Improvement of the Asymptotic Iteration Method for Exactly Solvable Eigenvalue Problems
We derive a formula that simplifies the original asymptotic iteration method
formulation to find the energy eigenvalues for the analytically solvable cases.
We then show that there is a connection between the asymptotic iteration and
the Nikiforov--Uvarov methods, which both solve the second order linear
ordinary differential equations analytically.Comment: RevTex4, 8 page
Joinability of Particulate Reinforced Alumix 231 Based Composite Materials Produced by Powder Metallurgy Route
In the present study, weldability of Alumix 231 based composite materials reinforced with Al₂O₃ and B₄C and produced by powder metallurgy route is investigated. Various amounts of (0, 5, 10, and 15% wt.)Al₂O₃ and B₄C powders are added to the pre-alloyed Alumix 231 (Al—2.5% Cu—0.5% Mg—14% Si) powders separately and then mixed in a three-dimensional mixer for 45 min. Powders are compacted and sintered in an argon atmosphere at 640°C for 4 h. Produced blocks are welded by the Tungsten Inert Gas (TIG) welding at 25 V, 197 A and 14 l/min shielded gas flow in commercially pure argon atmosphere. Macro- and microexamination together with some mechanical properties of the welded area are studied. The results show that, although high amount of particles resulted in a decrease in the density, these composite materials can still be welded by the TIG welding method successfully.Исследуется свариваемость произведённых методом порошковой металлургии композитных материалов на основе Alumix 231, армированных Al₂O₃ и B₄C. Различные количества (0, 5, 10 и 15 масс.%) порошков Al₂O₃ и B₄C по отдельности добавлялись в предварительно сплавленные порошки Alumix 231 (Al—2,5% Cu—0,5% Mg—14% Si), а затем перемешивались в трёхмерном миксере в течение 45 минут. Затем порошки прессовались и спекались в атмосфере аргона при 640°C в течение 4 часов. Полученные блоки сваривались вольфрамовой сваркой в атмосфере инертного газа при 25 В, 197 А и потоке инертного газа в 14 л/мин в атмосфере технически чистого аргона. Были проведены макро- и микроисследования некоторых механических свойств сварной зоны. Их результаты показали, что, хотя оказалось большое количество частиц с пониженной плотностью, эти композитные материалы могут быть успешно сварены методом вольфрамовой сварки в атмосфере инертного газа.Досліджується зварюваність вироблених методою порошкової металургії композитних матеріялів на основі Alumix 231, армованих Al₂O₃ і B₄C. Різні кількості (0, 5, 10 і 15 мас.% ) порошків Al₂O₃ і B₄C окремо додавалися у попередньо стоплені порошки Alumix 231 (Al—2,5% Cu—0,5% Mg—14% Si), а потім перемішувалися в тривимірному міксері впродовж 45 хвилин. Потім порошки пресувалися та спікалися в атмосфері арґону при 640°C впродовж 4 годин. Одержані блоки зварювалися вольфрамовим зваренням в атмосфері інертного газу при 25 В, 197 А та потоці інертного газу у 14 л/хв. в атмосфері технічно чистого арґону. Було виконано макро- та мікродослідження деяких механічних властивостей зварної зони. їх результати показали, що, хоча виявилася велика кількість частинок зі зниженою густиною, ці композитні матеріяли можуть бути успішно зварені методою вольфрамового зварювання в атмосфері інертного газу
Approximate solution of the Duffin-Kemmer-Petiau equation for a vector Yukawa potential with arbitrary total angular momenta
The usual approximation scheme is used to study the solution of the
Duffin-Kemmer-Petiau (DKP) equation for a vector Yukawa potential in the
framework of the parametric Nikiforov-Uvarov (NU) method. The approximate
energy eigenvalue equation and the corresponding wave function spinor
components are calculated for arbitrary total angular momentum in closed form.
Further, the approximate energy equation and wave function spinor components
are also given for case. A set of parameter values is used to obtain the
numerical values for the energy states with various values of quantum levelsComment: 17 pages; Communications in Theoretical Physics (2012). arXiv admin
note: substantial text overlap with arXiv:1205.0938, and with
arXiv:quant-ph/0410159 by other author
Approximate k-state solutions to the Dirac-Yukawa problem based on the spin and pseudospin symmetry
Using an approximation scheme to deal with the centrifugal
(pseudo-centrifugal) term, we solve the Dirac equation with the screened
Coulomb (Yukawa) potential for any arbitrary spin-orbit quantum number
{\kappa}. Based on the spin and pseudospin symmetry, analytic bound state
energy spectrum formulas and their corresponding upper- and lower-spinor
components of two Dirac particles are obtained using a shortcut of the
Nikiforov-Uvarov method. We find a wide range of permissible values for the
spin symmetry constant C_{s} from the valence energy spectrum of particle and
also for pseudospin symmetry constant C_{ps} from the hole energy spectrum of
antiparticle. Further, we show that the present potential interaction becomes
less (more) attractive for a long (short) range screening parameter {\alpha}.
To remove the degeneracies in energy levels we consider the spin and pseudospin
solution of Dirac equation for Yukawa potential plus a centrifugal-like term. A
few special cases such as the exact spin (pseudospin) symmetry Dirac-Yukawa,
the Yukawa plus centrifugal-like potentials, the limit when {\alpha} becomes
zero (Coulomb potential field) and the non-relativistic limit of our solution
are studied. The nonrelativistic solutions are compared with those obtained by
other methods.Comment: 21 pages, 6 figure
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