9 research outputs found
Optical potentials of halo and weakly bound nuclei
The optical potential of halo and weakly bound nuclei has a long range part
due to the coupling to breakup that damps the elastic scattering angular
distributions at all angles for which the effect of the nuclear interaction is
felt. In charge exchange reactions leading to a final state with a halo
nucleus, the surface potential is responsible for a strong reduction in the
absolute cross section. We show how the halo effect can be simply estimated
semiclassically and related to the properties of the halo wave function.
Assuming an exponential tail for the imaginary surface potential we show that
the most important parameter is the diffusness of the potential which
is directly related to the decay length of the initial wave function
by Comment: 18 Latex pages, 1 table, 1 eps figures, 3 ps figures. accepted to
Nucl. Phys.
The Quantum Liquid of Alpha Clusters
Within the variational approach of Bose liquids we analyze the g.s. energy of
charge neutral alpha matter at =0. As a prerequisite for such calculation we
take from the literature or propose new \alp-\alp potentials that are
particularly suitable for this task, i.e. posses a repulsive core and/or
reproduce the low energy scattering data and the resonance properties of the
\alp-\alp system. The alpha matter EOS is then obtained with the HNC method
using Pandharipande-Bethe correlation derived variationally in the lowest order
expansion of the energy functional or a simple gaussian function with a healing
range determined by the normalization of the radial distribution function in
the lowest order. We show that saturation is achieved only via repulsive and
shallow potentials that are not consistent with the scattering and resonance
constraints.Comment: 8 pages, 4 figure
Refractive effects in the scattering of loosely bound nuclei
A study of the interaction of loosely bound nuclei 6,7Li at 9 and 19 AMeV
with light targets has been undertaken. With the determination of unambiguous
optical potentials in mind, elastic data for four projectile-target
combinations and one neutron transfer reaction 13C(7Li,8Li)12C have been
measured on a large angular range. The kinematical regime encompasses a region
where the mean field (optical potential) has a marked variation with mass and
energy, but turns out to be sufficiently surface transparent to allow strong
refractive effects to be manifested in elastic scattering data at intermediate
angles. The identified exotic feature, a "plateau" in the angular distributions
at intermediate angles, is fully confirmed in four reaction channels and
interpreted as a pre-rainbow oscillation resulting from the interference of the
barrier and internal barrier farside scattering subamplitudes.Comment: 19 pages, 14 figures, 3 tables to submit to Phys. Rev.
Fraunhofer and refractive scattering of heavy ions in strong laser fields
Until recently the potential scattering of a charged particle in a laser field received attention exclusively in atomic physics. The differential cross-section of laser-assisted electron-atom collisions for n emitted or absorbed photons is provided by a simple law which casts the result as a product between the field-free value and the square of the Bessel function of order n with its argument containing the effect of the laser in a non-perturbative way. From the experimental standpoint, laser-assisted electron-atom collisions are important because they allow the observation of multiphoton effects even at moderate laser intensities. The aim of this study is to calculate the nucleus-nucleus differential cross section in the field of a strong laser with wavelengths in the optical domain such that the low-frequency approximation is fulfilled. We investigate the dependence of the n-photon differential cross-section on the intensity, photon energy and shape of the pulse for a projectile/target combination at a fixed collision energy which exhibits a superposition of Fraunhofer and refractive behavior. We also discuss the role of the laser perturbation on the near and farside decomposition in the angular distribution, an issue never discussed before in the literature. We apply a standard optical model approach to explain the experimental differential cross-section of the elastic scattering of 4He on 58Ni at a laboratory energy E = 139 MeV and resolve the corresponding farside/nearside (F/N) decomposition in the field-free case. We give an example of reaction in which Fraunhofer diffraction and refractive rainbow hump effects are easily recognized in the elastic angular distribution. Next, we apply the Kroll-Watson theorem, in order to determine the n -photon contributions to the cross-section for continuous-wave (cw) and modulated pulses. In the elastic scattering of heavy ions in a radiation field of low intensity, the amplitude drops by orders of magnitude with respect to the unperturbed case once the exchange of photons is initiated. For intensities approaching W/cm2 multiphoton effects become important. In the case of short laser pulses we conclude that the strength of n-photon contribution increases with the pulse duration
Double fine structure in the cluster radioactivity of "252Cf
Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
High-energy two-neutron removal from Be10
A kinetically complete measurement of the C12(Be10, α+α+n) and (Be10, α+α) reactions has been performed at a beam energy of 30 MeV/nucleon. The charged beam velocity particles were detected in an array of Si-CsI detectors placed at zero degrees, and the neutrons in an 81-element neutron array. The coincident detection of the final-state particles, produced in the breakup of Be10, allowed the reconstruction of the excitation energy in the Be8 and Be9 systems. States in Be8 were identified, in particular the ground and first-excited states; and in Be9, states at 1.68, 2.43, and (2.78, 3.05) MeV were observed. The population of these levels, in particular the 2.43 MeV 5/2- level, suggests that collective excitations play an important role in the neutron removal process. Distorted wave Born approximation and Glauber-type calculations have been used to model the direct neutron removal from the Be10 ground state and the two-step removal via inelastic excitations of the Be10(2+) and Be9(5/2-) excited states. © 2005 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe