J. E. Draper

Neutron transfer reactions with very heavy ions

Abstract We have studied neutron transfer reactions induced by 132Xe on three rare-earth targets at E V C ∼ 1.1 . By using particle-particle-γ coincidence techniques we were able to identify final products and states populated in the one- and two-neutron reactions. The dependence of the transfer probabilities on the distance of closest approach is discussed in terms of effective penetration factors. The results seem to indicate the importance in two-neutron transfer of intermediate states with ≳ 6 MeV of excitation energy. The effect of excitation energy on the enhancement of the two-neutron transfer is discussed. A qualitative interpretation of the spin dependence of the one-neutron γ-ray yields in terms of the spatial localization of the wave functions involved is given.

Superdeformed bands in Nd nuclei

Abstract Superdeformed bands were found in 134, 136 Nd. Their dynamic moments of inertia are about as large as those of the known superdeformed bands in 135 Nd and 132 Ce, corresponding to β ≈ 0.5. A high probability for staying in band is measured for the discrete superdeformed bands in 134, 136 Nd, in contrast to the unresolved superdeformed ridges.

New structures at high spin in 159Er

Abstract The nucleus 159 Er was studied with the HERA γ-ray spectrometer. Three rotational bands were extended to higher spins, and three new bands were found. It is shown that specific orbitals rather strongly influence the high-spin behavior, some states remaining collective (somewhat triaxial), others evolving towards a non-collective oblate structure. One of the new bands is a higher- K band, similar to those found in heavier nuclei.

Particle-hole states at high spin in 150Dy

Abstract The level scheme of the nucleus 150 Dy up to spin around 40 was obtained using the reaction 114 Cd( 40 Ar, 4n). Above spins 20 to 22 — the highest obtainable from the valence nucleons — the breaking of the 146 Gd pproton and neutron cores occurs in separate parallel cascades.

Mass dependence of shell effects at high rotational frequencies

Abstract The continuum γ-ray spectra from the reactions 40 Ar(170–185 MeV) + 50 Ti, 68 Zn, 82 Se, 100 Mo → 90 Zr ∗ , 108 Cd ∗ , 122 Te ∗ , 140 Nd ∗ , respectively have been studied by using a sum-energy technique. The evolution of the γ-ray spectra with sum energy (spin) suggests the presence of rotational motion at high spins. A method to correct for incomplete feeding was applied to the γ-ray spectra and effective moments of inertia were determined. The results indicate the appearance of a new source of angular momentum at high rotational frequencies. We interpret this as the alignment of high- j orbitals from the next major shell. Simple arguments, as well as cranked-shell-model calculations, are consistent with this picture. Data on band moments of inertia, from E γ − E γ correlation experiments, are also in accord with our interpretation.