A. K. Basak

Non-monotonic potential description of alpha–Zr refractive elastic scattering

Experimental differential cross sections of α elastic scattering by 90Zr in the 15.0–141.7 MeV range of the bombarding energies have been analysed within the framework of an optical model using non-monotonic (NM) potentials. These potentials are generated from the energy-density functional theory using a realistic two-nucleon potential coupled with an appropriate consideration of the Pauli principle. The NM nature of the real part of the potential seems to be gradually diminishing at energies beyond 118.0 MeV. The Airy structure of the nuclear rainbow scattering data in the energy range of 79.5–141.7 MeV is for the first time well accounted for by the shallow NM potential. Two potential families, which are located in the real part, bear a linear variation of a volume integral in the energy range 25.0–141.7 MeV with a threshold anomaly at the lower energies. The potential contains an interior repulsive part that, with energy, shifts towards the surface and gradually weakens until it is almost lost in the nuclear surface. The requirement of a deep attractive real part of the nuclear potential seems to be generally non-stringent for describing the nuclear rainbow oscillations. Some discrete ambiguities in the potentials seem to persist even when the ‘exponential falloff’ in the angular distribution following the ‘rainbow angle’ is well reproduced in this investigation using the NM real part of the optical potentials.

NON-MONOTONIC ALPHA- AND 6Li-POTENTIALS FROM ENERGY DENSITY FUNCTIONAL FORMALISM

The present status of the α-nucleus potential, generated from the energy density functional (EDF) formalism using a realistic two-nucleon potential, which incorporates the Pauli principle, is discussed. The EDF potentials, calculated using a density distribution of α-particle that yields a binding energy of 20 MeV with a reasonable root-mean-squared radius and observed density distributions of 6Li and various target nuclei, are found to be shallow and non-monotonic in character. This non-monotonic EDF potential reproduces satisfactorily the experimental elastic scattering data, particularly at energies above the Coulomb barrier. Since the elastic scattering data and the binding energies of all nuclei considered herein are well reproduced using the mean field generated from a realistic two-nucleon potential for nuclear and nucleonic matter, one may conclude to have reasonable information on the equation of states of nuclear and nucleonic matter from a very low to the saturation density from the present investigation.

ALPHA-ALPHA AND ALPHA-NUCLEUS POTENTIALS: AN ENERGY-DENSITY FUNCTIONAL APPROACH

The real parts of the alpha-alpha and alpha-nucleus potential, particularly for 40,44,48Ca and 58Ni targets are determined from a realistic two-nucleon potential using an energy-density functional approach and are found to be non-monotonic with a short range repulsion in their functional forms that are similar to those needed in accounting for elastic scattering data. The deduced alpha-alpha potential has no bound states and the calculated decay width of 8Be of about 6.4 eV at about 200 keV energy is in agreement with the measurement.

Normalization constant of the (α, t) reaction

SummaryThe DWBA analyses are performed for the ground states and other strong transitions populated in the (α, t) reaction on various targets ranging fromA = 16 to 208 with zero-range and with finite-range corrections in the local energy approximation (LEA). The normalization constants without and with the LEA are found to be, respectively,D20 = (18.16±3.49) × 10 MeV fm andD = (8.67±1.60)× 10 MeV2 fm3 which are reasonably consistent with some other previous studies. The normalization constants for the (α, t) reaction on the Al target are also deduced for different incident energiesEα = 25.0, 25.2, 64.5, 80.0 and 104.0 MeV for studying any possible energy dependence of the normalization constant. No tangible energy dependence was found in the present study and hence the LEA seems to be valid reliably within the energy range studied. The ratioD20/D bears a value of about 2.0 which is remarkably constant over the target masses and incident energies.