Surface diffuseness parameter for systems withZPZT≃780

Abstract

We have investigated experimental quasielastic cross sections measured at backward angles and at deep sub-barrier energies for the 35 Cl+ 105,106,110 Pd and 32 S+ 110 Pd systems. Since coupling effects are almost negligible at very low bombarding energies, the quasielastic data allow one to determine the diffuseness parameter of the ion-ion potential. For the analyzed reactions we have obtained a surface diffuseness parameter value around 0.58 ± 0.04 fm. PACS number(s): 25.70.Bc, 24.10.Ht Recently, Washiyama and collaborators [1] have proved that large-angle quasielastic scattering measurements performed at deep sub-barrier energies are a useful tool for the investigation of the diffuseness parameter in nucleus-nucleus potentials. The idea rests on the fact that the channel coupling effects on the quasielastic scattering may be neglected at these low energies [2]. In this way, one can use the simple one-dimensional optical potential with a Woods-Saxon shape for its real partin order to extract the potential depth V 0 , the radius parameter r 0 , and the surface diffuseness a. (Imaginary potentials account for the absorption processes.) However, the extraction of an optimum set of parameters from the fit of the calculated cross sections to the experimental values is not unambiguous. In Ref.[1], the resulting ambiguities have been circumvented by imposing the condition that the barrier height be constant and equal to the value calculated using the Akyüz-Winther parametrization (AW) [3]. The diffuseness was then taken as the only free parameter while the potential radius and/or depth parameters were chosen so as to fulfill the abovementioned constraint. By doing so, Washiyama and co-authors could investigate the behavior of the optimum diffuseness for different reaction systems. The main conclusion of their work was that standard values close to a = 0.63 fm are generally adequate to explain the experimental results for systems consisting of spherical nuclei, whereas higher values in the range of 0.8 to 1.1 fm are required if deformed nuclei are involved. These values are consistent with those obtained from fusion data [4,5] although it has also been proposed the use of an energy-dependent radius of the potential [6] to explain the measured fusion cross sections. The purpose of this Brief Report is to contribute to the understanding of the role played by the surface diffuseness parameter in heavy-ion reactions through the analysis of available * Electronic address: capurro@tandar.cnea.gov.ar quasielastic data for reactions involving spherical nuclei whose Z P Z T product is near 780. We have analyzed quasielastic scattering cross sections measured at backward angles for the 35 Cl + 105,106,110 Pd and 32 S + 110 Pd systems at energies well below the Coulomb barrier [7,8]. All these palladium-isotope targets exhibit vibrational characteristics. It should be noted that the original aim of these measurements was to extract a representation of the fusion-barrier distribution and, as a consequence, some limitations (su...

Quasi-elastic backscattering of 6,7Li on light, medium and heavy targets at near- and sub-barrier energies

“…For further understanding this subject and being able to energy map the potential, other complementary means to the conventional techniques should be also adopted. As such, the application of elastic backscattering [7] was recently suggested in [8,9], while its role for probing properties of the optical potential and the structure of the involved nuclei has been extensively demonstrated in recent years [10][11][12][13][14][15][16][17].…”

Near-barrier quasielastic scattering as a sensitive tool to derive nuclear matter diffuseness

“…Some works have been dedicated to derive the interacting potential diffuseness for different systems from deep subbarrier quasielastic scattering data at backward angles, as, for example Refs. [4][5][6][7][8][9]. The derivation of the NMD from this kind of work is a difficult task, since the interacting potentials of Woods-Saxon form have several parameters and consequently have large ambiguities.…”

Probing the potential and reaction coupling effects ofLi6,7+Si28Zerva1, Pakou2, Rusek3 et al. 2010Phys. Rev. C285150View full textAdd to dashboardCite

“…A large amount of work has been devoted to systematic studies of the surface properties of the optical model potential (diffusivity of Woods-Saxon potentials) through high-precision backward-angle quasielastic scattering measurements [8][9][10][11][12][13] at sub-barrier energies. At these backward angles, deviations from unity of the ratio to Rutherford of the (quasi)elastic cross sections are mainly sensitive to the surface properties of the potential [9].…”