No abstract available

No abstract available

[en] Short communication

[en] Short communication

[en] The superdeformed nucleus ¹⁹³Pb has been studied following a heavy-ion fusion-evaporation reaction with the Gammasphere spectrometer array. Three new superdeformed bands, two of them probably signature partners, have been observed, bringing the total number of superdeformed bands known in this nucleus to nine. An estimate of the g-factor associated with one of the previously known pairs of strongly coupled excited bands has been made, confirming their configuration. The properties of the bands are compared with the results of cranked shell model calculations; good agreement is found and configurations are assigned to each band. The two new signature partner bands are suggested to be based on the two signatures of the [512]5/2 neutron orbital. The third new band is probably based on the 7₃ intruder orbital. In addition, the high-energy region of the spectrum in coincidence with the yrast superdeformed bands has been carefully studied. The current data provide no evidence for the previously reported transitions linking the superdeformed and normal-deformed states with energies around 2.2-2.4 MeV

[en] Full text: A recently developed two-level mixing model of the transition from superdeformed to normal-deformed nuclear shape is applied to evaluate the tunnelling width of the decay-out process in ¹⁹²Pb, ¹⁹⁴Pb and ¹⁹⁶Pb. We estimate the level densities and gamma-decay widths for the normally-deformed states at the excitation energy of the decay, and use observed properties of the superdeformed states as input for the model. The relationship between the extracted widths and the potential barrier between the shapes is discussed. Copyright (2005) Australian Institute of Physics

[en] An experiment aimed at studying high-spin states in ¹⁹⁰Hg was performed with the Eurogam II array. The data have revealed the presence of cascades of magnetic dipole transitions with some unexpected properties. Unlike the M1 bands previously observed in the heavier Hg isotopes, these structures have extremely large B(M1)/B(E2) ratios. The observation of a third dipole hand with much lower B(M1)/B(E2) values in the same spin/excitation energy regime suggests that the bands may represent configurations occurring in different minima in the potential energy surface. Configuration-dependent Cranked Nilsson-Strutinsky calculations predict the presence of a minimum in the nuclear potential energy surface at a deformation of (var_epsilon) 0.2, γ -90^o, occurring when a proton is excited across the Z = 82 shell-gap into an h_o□/₂ orbital. It is suggested that the bands exhibiting anomalously large B(M1)/B(E2) ratios may be associated with this minimum

[en] Full text: The radon isotopes with neutron numbers close to the N=126 closed shell are useful for testing the shell model for increasing numbers of valence particles. The nucleus²⁰⁹Rn displays shell model characteristics with fragmented high spin states. Previously, ²⁰⁴Rn and ²⁰⁶Rn were examined in the context of the shell model, while ²⁰⁵Rn has a cascade of magnetic dipole transitions that has been interpreted as a shears band. We have carried out studies of ^204-207Rn using the CAESAR array at the ANU. The results of these experiments will be presented

[en] Full text: Although rotational bands in superdeformed nuclei have been known for almost twenty years, experimental information about these states remains very limited This is primarily because of the difficulties encountered in identifying the γ-ray decay pathways by which the nucleus changes from the superdeformed shape to more normal (less deformed) nuclear shapes Without such information, fundamental properties of the superdeformed nucleus such as excitation energy and spin are unknown Recent work establishing the excitation energy and spin of the yrast superdeformed band in ¹⁹⁶Pb will be presented, and the results compared to data in neighbouring nuclei and theoretical predictions. Copyright (2005) Australian Institute of Physics

No abstract available