The program of spectroscopic studies underway in the Department covers several related areas. At present, one of our main focuses is the study of deformed nuclei close to stability, in a region where multi-quasiparticle intrinsic states compete with rotational excitations. In collaborative work with groups in the United States of America and the United Kingdom, we are involved in identifying and characterizing multi-quasiparticle high-K states in nuclei with masses around A=150-170, the aim of which is to provide more comprehensive information on both decay anomalies and configuration effects on rotation.
The most efficient way to populate high angular momentum states in heavy nuclei close to the valley of stability is via the use of multi-nucleon transfer (or deep inelastic) reactions. Such reactions often require higher beam energies than can be achieved using the 14UD accelerator alone, and thus development of the Department's LINAC, which will provide heavy beams at suitable energies, is of great importance. Combining multinucleon transfer reactions with our expertise in isomer spectroscopy and the flexibility of our beam pulsing system will provide a powerful tool for spectropscopic studies of stable and neutron-rich nuclei.
Our long-standing studies of shape co-existence in the neutron-deficient lead isotopes have also developed. Substantiation of the enhanced E3 decays proposed previously has redirected our attention to anomalous rates observed for specific spin-flip proton transitions in both lead and polonium isotopes, which we have now interpreted as new evidence for oblate deformations. The experimental program at ANU is being further enhanced with the developed of a new gamma-ray and electron detection system, based around the SOLITAIRE spectrometer developed by the Nuclear Reactions group. This device will allow us to study the decay of long-lived states in nuclei produced in reactions with a large fission cross-section, and thus will be a powerful tool for spectroscopic studies in the light lead region.
Another area which has recently yielded some interesting results is the study of superdeformed states in nuclei with A~190. These states have been the subject of great theoretical and experimental interest since their first observation in the late 1980s, and hundreds of examples have now been observed. However challenges in their experimental study have meant that it has only been possible to measure the most basic of their properties - the excitation energy, angular momentum and parity - in a half dozen of cases. Of these, the two most recent measurements were made by members of this Department. The results provide the first step towards a systematic study of the excitation energies and pave the way towards characterisation of the so-called superdeformed magic numbers.
The evaluation of nuclear structure data for science and technology is a recent addition to our activity. The new conversion coefficient calculator, BrIcc has been developed in the group in international collaborations with laboratories in the USA and USSR.
The Nuclear structure group welcomes requests from research groups or individuals interested in exploring the possibility of establishing new collaborations that could exploit the unique resources and instumental capabilities of the laboratories.