G. Madurga

Exponential optical potentials for heavy-ion elastic scattering

Abstract A detailed quantitative survey of the optical-model ambiguity in some particular cases shows a very wide range of equally good choices in the Woods-Saxon parameters and even some degree of indefiniteness in the magnitudes usually considered to be well-defined, like the strong absorption radius. In 16O + 208Pb elastic scattering we show that all the good real potentials agree over a given region rather than a point. A systematic use of (real and imaginary) exponential potentials can fit, in a less redundant form, a fairly sizable range of experimental data and lends itself to the construction of a general expression.

Nuclear-structure dependence of the fusion cross section for heavy ions

Abstract The energy dependence of the fusion cross section and its maximum value are well predicted, for a wide range of nuclei and energies, by introducing information on the nuclear matter density distribution into a simple formula.

Critical radii for alpha-particle elastic scattering

Abstract The critical radii obtained from analyses of the elastic scattering of alpha-particles by a range of nuclei are found to be closely connected with the nuclear matter distributions obtained by summing the squares of single-particle wavefunctions. This provides a method of calculating the details of the optical potentials from the structure of the target nucleus.

The role of rainbow refraction in heavy ion elastic scattering

The energy dependence of both the strong absorption radius, Rsa, and the rainbow distance, Rr, in the elastic scattering of a dozen pairs of heavy ions is studied. Rsa decreases with energy linearly in E−13 while Rr increases linearly in E−32. The rainbow effect appears to prevail (Rr > Rsa) above a certain energy which is proportional to the product Z1Z2.

A level-density-dependent imaginary potential for heavy ions☆

Abstract Under the assumption that compound-nucleus formation is the only channel competing with elastic scattering, an L -dependent imaginary potential is defined with the help of the compound-nucleus level density. For the latter an expression is used which seems to be accurate enough for excitation energies of several tens of MeV and with a substantial part of rotational energy. Associated with a double-folded real part, this imaginary potential is shown to reproduce well the elastic scattering data of eight systems of medium size (total mass between 36 and 72) at various energies not very high above the Coulomb barrier. The results are equivalent to those obtained with a folding real potential and a Woods-Saxon imaginary potential with parameters adjusted for each set of data with the advantage that our approach only needs two parameters to fit the data for a wide range of energies for each scattering system.

A phenomenological imaginary part of the optical potential for heavy ions

Abstract The depth of the imaginary part of the optical potential is derived from the assumption that, at a given energy and for each partial wave L, it is proportional to the compound nucleus density level up to a given excitation energy above the yrast level corresponding to the angular momentum L , and remains a constant for smaller values of L . The prescription is successfully tested for the system 16 O + 28 Si at nine different projectile energies between 33 and 81 MeV; it fails however at 141.5 MeV, as expected, because other channels, besides elastic scattering and fusion, are important.

Consistent description of the experimental root mean square charge radii

The authors present an analysis of the effect of the long-range residual interaction (LRRI) on the root mean square radius of charge (RMS radius) over a large range of nuclear masses. They also investigate the implications of a consistent treatment of that effect on single-particle potentials and energies.