A level-density-dependent imaginary potential for heavy ions

Polarization effects due to coupling of elastic to compound states

“…The resulting imaginary potential is strongly energy and angular momentum dependent, this dependence primarily arising from the expression for the compound nucleus level density. Treating the real part of the nucleus-nucleus potential as given by the double folding potential, the derived imaginary potential was seen to be able to reproduce the elastic scattering of several systems at energies not far above the Coulomb barrier [ 2].…”

“…The resulting imaginary potential is strongly energy and angular momentum dependent, this dependence primarily arising from the expression for the compound nucleus level density. Treating the real part of the nucleus-nucleus potential as given by the double folding potential, the derived imaginary potential was seen to be able to reproduce the elastic scattering of several systems at energies not far above the Coulomb barrier [ 2].It was shown recently that the optical potentials that describe the elastic scattering of '60 by 2°Spb [3] and 6°Ni [4] behave in an apparently anomalous fashion at energies approaching the Coulomb barrier, The imaginary potential decreases sharply in magnitude as the energy approaches the Coulomb barrier and simultaneously the real potential varies strongly with energy at these energies. This energy dependence of the real and imaginary parts of the optical potential was shown to be consistent with the Work partially supported by the Spanish Comisi6n Asesora de lnvestigaci6n Cientifica y Trcnica, contract number 2868-83. dispersion relation [ 5 ] which connects the real and imaginary parts of the optical potential [ 6].…”

“…This energy dependence of the real and imaginary parts of the optical potential was shown to be consistent with the Work partially supported by the Spanish Comisi6n Asesora de lnvestigaci6n Cientifica y Trcnica, contract number 2868-83. dispersion relation [ 5 ] which connects the real and imaginary parts of the optical potential [ 6]. In general, the dispersion relation predicts that if the imaginary potential rises rapidly with energy over a small range of energy, the associated contribution to the real potential will be attractive in the same energy range.The angular-momentum-and energy-dependent imaginary potential derived by allowing for the compound nucleus to take flux away from the elastic channel [ 1,2] would thus be expected to give rise to a L-dependent and energy-dependent real polarization potential.In this work we apply the dispersion relation to investigate this real polarization potential for the scattering of 160 by 24Mg, 285i and 4°Ca.A generalized optical potential which, incorporated in a one-body Schr6dinger equation, describes the elastic scattering of two nuclei was first formally introduced for nucleon-nucleus scattering by Feshbach [ 5]. In general, the optical potential will be complex, non-local and energy dependent.…”

“…The angular-momentum-and energy-dependent imaginary potential derived by allowing for the compound nucleus to take flux away from the elastic channel [ 1,2] would thus be expected to give rise to a L-dependent and energy-dependent real polarization potential.…”

“…We shall, following refs. [ 1,2], assume that the only channels competing with elastic scattering are the compound nucleus channels. The resulting imaginary potential can be expressed in the form…”