Evolution of collective and noncollective structures in Xe-123

An experiment involving a heavy-ion-induced fusion-evaporation reaction was carried out where high-spin states of 123Xe were populated in the 80Se (48Ca,5n) 123Xe reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the addition of five new band structures and several interband transitions. Cranked Nilsson-Strutinsky (CNS) calculations were performed and compared with the experimental results in order to assign configurations to the bands.Additional co-authors: T Lauritsen, S Zhu, A Korichi, P Fallon, B M Nyakó, and J Timá

Highly deformed band structures due to core excitations in 123Xe

High-spin states in 123 Xe were populated in the 80 Se(48 Ca, 5n) 123 Xe reaction at a beam energy of 207 MeV. Gamma-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus.The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. It is concluded that the configurations of the bands involve two-proton excita-tions across the Z = 50 as well as excitation of neutrons across the N = 82 shell gaps resulting in a large deformation, ε2 ∼ 0.30 and γ ∼ 5 • .Additional co-authors: F. G. Kondev, T. Lauritsen, S. Zhu, A. Korichi, P. Fallon, B. M. Nyakó, and J. Timá

Superdeformed nuclei

This paper reviews the most recent advances in the understanding of the physics of superdeformed nuclei from the point of view of the experimentalists. It covers among other subjects the following topics: (1) the discovery of a new region of superdeformed nuclei near A=190, (2) the surprising result of the occurrence of bands with identical transition energies in neighboring superdeformed nuclei near A=150 and A=190, (3) the importance of octupole degrees of freedom at large deformation and (4) the properties associated with the feeding and the decay of superdeformed bands. The text presented hereafter will appear as a contribution to the Annual Review of Nuclear and Particle Science, Volume 41. 88 refs., 11 figs

Motional narrowing and ergodic bands in excited superdeformed states of 194Hg

International audienceThe Egamma-Egamma coincidence spectra from the electromagnetic decay of excited superdeformed states in 194Hg reveal surprisingly narrow ridges, parallel to the diagonal. 100-150 excited bands are found to contribute to these ridges, which account for nearly all the unresolved E2 decay strength. Comparison with theory suggests that these excited bands have many components in their wavefunctions, yet they display remarkable rotational coherence. This phenomenon can be explained in terms of the combination of shell effects and motional narrowing

Candidate superdeformed band in 28Si

Recent antisymmetrized molecular dynamics (AMD) calculations for 28Si suggest the presence of a superdeformed (SD) band with a dominant 24Mg + α clustering for its configuration, with firm predictions for its location and associated moment of inertia. This motivates a review of the experimental results reported in the literature with a particular focus on 24Mg(α,γ ) studies, as well as on α-like heavy-ion transfer reactions such as 12C(20Ne,α) 28Si. Combining this information for the first time leads to a set of candidate SD states whose properties point to their α-cluster structure and strong associated deformation. Analysis of data from Gammasphere allows the electromagnetic decay of these candidate states to be probed and reveals further supporting evidence for such a structure. This paper appraises this body of information and finds the evidence for an SD band is strong.peerReviewe

In-beam spectroscopy with intense ion beams: Evidence for a rotational structure in 246Fm

The rotational structure of 246Fm has been investigated using in-beam γ -ray spectroscopic techniques. The experiment was performed using the JUROGAMII germanium detector array coupled to the gas-filled recoil ion transport unit (RITU) and the gamma recoil electron alpha tagging (GREAT) focal plane detection system. Nuclei of 246Fm were produced using a 186 MeV beam of 40Ar impinging on a 208Pb target. The JUROGAMII array was fully instrumented with Tracking Numerical Treatment 2 Dubna (TNT2D) digital acquisition cards. The use of digital electronics and a rotating target allowed for unprecedented beam intensities of up to 71 particle-nanoamperes for prompt γ -ray spectroscopy at a level of approximately 11 nb. With all these major experimental advances a rotational band is observed in 246Fm.peerReviewe

Shell-Structure and Pairing Interaction in Superheavy Nuclei: Rotational Properties of the Z=104 Nucleus 256Rf

The rotational band structure of the Z ¼ 104 nucleus 256Rf has been observed up to a tentative spin of 20@ using state-of-the-art -ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at Z ¼ 104, which is predicted in a number of current self-consistent mean-field models.peerReviewe