Y. Kondō

A unique deep potential for the 16O+16O system

We have reanalysed the recently observed nuclear rainbow data for the 16O+16O system and have demonstrated that there are three optical potentials which fit the data equally well. This discrete ambiguity originates from the limited angular range of the data. By taking into account the results of a recent analysis of low-energy resonant phenomena in this system and the dispersion relation between the real and imaginary parts of the optical potential, a unique selection of the potential set can be made.

A deep potential description of the 16O+16O system

Abstract Resonant phenomena in the 16 O+ 16 O system are described successfully in terms of an ion-ion potential which is sufficiently deep to support wavefunctions with the proper number of radial nodes, consistent with the Pauli principle. Possible candidates for quasimolecular states in 32 S are indicated.

Transfer contribution to elastic 16O + 20Ne scattering and parity-dependent interactions

Abstract Gross resonant structures observed in the 20 Ne ( 16 O, 16 O) 20 Ne (gs) excitation function at θ CM =154°±2° are successfully described by calculations in which elastic α-transfer amplitudes are coherently added to elastic scattering amplitudes. It is shown that the effects of the α-transfer amplitudes are well simulated by the explicit inclusion of a parity-dependent term in the real potential in optical-model calculations of the elastic scattering.

The 20Ne(16O,16O)20Ne excitation function at θc.m. = 90° and parity-dependent interactions

Abstract The excitation function for 16 O + 20 Ne elastic scattering at θ c.m. = 90° has been measured over the energy range 21.5 MeV E c.m. 16 O− 20 Ne potential. A satisfactory description is obtained of elastic scattering excitation functions at θ c.m. = 90° and θ c.m. = 154° ± 2° with a potential which is deeper for even than for odd partial waves. Such a parity dependence is consistent with the assumption that this term arises from a requirement to simulate the effects of α-transfer amplitudes, and with the expectations of models which argue that parity dependence is to be expected as a consequence of the Pauli principle.

Coupled-channel description of resonant structures in the 16O + 20Ne system

Abstract Gross resonant structures observed in elastic scattering, inelastic scattering and the total reaction cross section for the 16 O + 20 Ne system have been studied successfully using a coupled-channel approach, within a symmetric rotor model, with the diagonal potential modified to include both a parity-dependent real interaction and an angular-momentum ( J )-dependent absorptive term. It is shown that the inclusion of both these terms is essential for the prediction of the four correlated gross structures observed in the energy range 23 MeV ≦ E c.m ≦ 38 MeV for both elastic and inelastic scattering excitation functions at backward angles. Each of the gross structures is modelled as a doublet of even-parity plus odd-parity resonances, which arise as a consequence of the parity-dependent interaction and which are enhanced by the J -dependent absorptive form. The elastic and inelastic scattering angular distributions at a number of energies are also well described. It is demonstrated that the inclusion of strong coupling overcomes a number of inadequacies noted in previous optical-model calculations for the 16 O + 20 Ne system. The total angular momenta of the resonant states obtained in the coupled-channel calculations are higher than those extracted from calculations which ignore coupling.

A deep optical potential and gross resonant structures in low energy 16O + 12C scattering

Abstract The gross structures observed in the fusion excitation function and the elastic scattering excitation functions for low energy 16 O + 12 C scattering are described successfully by using the optical potential model with a deep real part. The observed fusion oscillations are interpreted as a superposition of at least two potential resonance bands whose adjacent members coincide in energy.

Direct evidence for rapid energy dependence of the nucleus-nucleus interaction near the barrier radius at low energy

Abstract We show that a consistent description of 16 O(α, α 0 ) scattering close to the Coulomb barrier can be achieved only if (1) the interaction is made slightly angular momentum dependent; (ii) the surface of the potential is significantly less diffuse than that needed to describe the scattering data at higher incident energies. The second feature agrees qualitatively with recent theoretical predictions invoking either antisymmetrization or dispersion relation effects.

Shape resonances and deep optical potentials: A mean-field description of 12C + 12C scattering at low energies

Abstract A critical review is given of the features of 12 C + 12 C elastic scattering at low energies (Ecm ⩽ 37.5 MeV) which may be ascribed to a mean field, or optical potential, and how this field matches smoothly on to optical model descriptions of the scattering at higher energies (Ecm from 35 to 725 MeV). In particular we examine the proposed shape resonance band at low energy and show that it follows naturally from the use of a deep optical potential such as is required at higher energy. Furthermore we show that such a potential results in radial wavefunctions with sufficient numbers of nodes to satisfy the requirements of the Pauli principle under antisymmetrization. The reported reaction cross section data appear to be too small and inconsistent with the elastic cross sections measured in the same energy range; in addition, their oscillations with energy are too large in amplitude to be ascribed to spherical mean field effects. Some discussion is also given of the bound states implied by these potentials and their relation to a cluster model of 24Mg.

Analysis of resonant structures in the 16O+20Ne system using a deep optical potential and the LCNO model

Abstract Gross resonant structures observed in excitation functions in elastic scattering for the 16 O+ 20 Ne system have been described successfully using a deep potential within the framework of the LCNO model. The elastic scattering angular distributions at a number of energies are also well described. It is found that the parity-dependent potential obtained naturally within the LCNO model agrees in sign but has a longer range than that estimated in microscopic studies.

The parity-dependent potential for the 16O+20Ne system using the LCNO model

Abstract A parity-dependent potential for the 16 O+ 20 Ne system has been derived using the linear combination of nuclear orbitals (LCNO) model. This potential agrees in both sign and order of magnitude with the phenomenological parity-dependent potential derived previously for this system. The α -clustering of 20 Ne (g.s.) is shown to have a strong effect on the range of the parity-dependent potential.