J. R. B. Oliveira

Competing mechanism for generating high spin excitations in γ-soft nuclei: the 136Nd case

Abstract High-spin structures in 136Nd have been investigated via the 110Pd(30Si,4n) reaction at 125 MeV using the GASP array. Several bands consisting of stretched quadrupole transitions were identified. Two of them reach spins comparable to those of the highly-deformed (HD) band in 136Nd, which is based on a neutron i 13 2 - h 9 2 f 7 2 configuration. Total routhian surface (TRS) calculations indicate that regular high-spin excitations in this γ-soft nucleus, can be also generated through successive pairs of h 11 2 protons and neutrons coupled to a stable small-deformation triaxial core. The previously reported γ-ray transitions of an excited HD band, identical to the yrast HD band, are not confirmed by our data.

Study of the rainbow-like pattern in the elastic scattering of 16O on 27Al at Elab. = 100 MeV

Recently, a rainbow pattern in the elastic scattering of 16O + 27Al at Elab. = 100 MeV was reported. In the present paper, we show that the predicted change of slope of the cross section, as a function of angle, is mostly due to the far-side component of the scattering, which is affected by the inelastic couplings. The experimental data is consistent with the calculations up to the inflection point, where the effect of the couplings is significant. New experimental data, in very good agreement with the theoretical expectations around the Coulomb rainbow angle, are also presented.

ONSET OF COLLECTIVITY IN NEUTRON-DEFICIENT PO-196,PO-198

We have studied via in-beam gamma-ray spectroscopy Po-196 and Po-198, which are the first neutron-deficient Po isotopes to exhibit a collective low-lying structure. The ratios of yrast state energi ...

Nuclear structure in odd-odd nucleus 138 Pr

With the view of extending the systematics of odd-odd Pr nuclei toward the N=82 closed shell, high-spin states in 138Pr nucleus have been investigated with the 128Te(14N, 4nγ) reaction. Configurations and spin assignments are suggested for three of the observed band-structures.

Measurement of fusion cross sections for 16O+16O

In earlier works, the fusion cross section for the 16O+16O reaction has been measured using different techniques. In the present work, we have obtained an experimental excitation function for 16O+16O using γ-ray spectroscopy. The measurements were performed at center-of-mass energies between 8.28 and 12.25 MeV. The theoretical predictions obtained with a coupled-channel model are consistent with the experimental data. From our analyses, the extrapolated S-factor value at 6.6 MeV, corresponding to the Gamow peak energy for core oxygen burning conditions, is about 3.6 × 1025 MeV barn.

Elastic and inelastic angular distributions of the 7Li+120Sn system for energies near the Coulomb barrier

The reaction of 7Li+120Sn has been measured at bombarding energies of 21, 24 and 27 MeV. The -ray transition in 120Sn was observed and the angular distribution for the 2+ excited state was obtained. Coupled channels and coupled-reaction channels calculations, including the dynamical polarization potential due to the projectile break-up, obtained from continuum discretized coupled channel calculations, were performed. The comparison between the existing experimental elastic angular distribution with the coupled-reaction channels calculations indicates that the 1n stripping transfer is the most intense channel to be coupled and the 2n stripping reaction occurs sequentially rather than directly, however, further data must be analyzed to confirm this indication. The experimental elastic and inelastic scattering data were well described by the calculations, but some discrepancies in these channels may indicate the need for corrections to the nuclear potential and/or the necessity to incorporate further channels.

The role of couplings in nuclear rainbow formation at energies far above the barrier

A study of the 16O+28Si elastic and inelastic scattering is presented in the framework of Coupled Channel theory. The Sao Paulo Potential is used in the angular distribution calculations and compared with the existing data at 75 MeV bombarding energy. A nuclear rainbow pattern is predicted and becomes more clear above 100 MeV.

Nuclear Structure far from stability at the N = 50 Shell Closure

Medium and high spin states of the nuclei close to the N = 50 shell closure are investigated using deep inelastic and multi‐nucleon transfer reactions. New excited states of the nuclei 81Ga, 82Ge and 83As at N = 50 shell closure have been identified by means of the 82Se+238U reaction. Gamma rays have been acquired using the PRISMA‐CLARA setup of the Laboratori Nazionali di Legnaro, Italy (LNL).

In-beam gamma ray spectroscopy of 58Co

The odd-odd 58Co nucleus has been studied with the 51V(10B, p2n) reaction at 33-MeV incident energy and the g-spectrometer Saci-Perere. Excited states up to 8.0 MeV and spin up to 11+ have been observed. The results are compared to Shell Model calculations using the GXPF1 effective interaction, developed for use in the fp shell. The pf7/2-1An(p3/22f5/21) configuration was assigned to the yrast levels.

Important role of projectile excitation in

The elastic scattering angular distribution of the