[en] In-beam γ-ray spectroscopic studies of superdeformed bands in the mass 190 region are discussed with emphasis on recent results for Tl nuclei. Among those results, superdeformation at the edge of the region (in ¹⁸⁹Tl) and the first measurement of a superdeformed quadrupole moment in an odd-Z nucleus (¹⁹¹Tl) is presented. The experiments were conducted with the Gammasphere array at the Lawrence Berkeley National Laboratory. They are examples for the type of physics addressed in the first phase of Gammasphere operation

[en] The doubly-odd nucleus ¹⁶⁴Tm was studied in the ¹⁵⁰Nd(¹⁹F,5n) reaction at 85 MeV. Γ-ray spectroscopic measurements with the NORDBALL detector system were performed. The proposed level scheme of ¹⁶⁴Tm consists of six new and three known but reinvestigated rotational bands, which are based on either the K^π = 6^- isomer of the K^π = 1⁺ ground state. Most of these bands show the common feature of a very small signature splitting (Δe' ∼ 0 at ℎω =0.15 MeV). Therefore, a discussion of the experimental results in the framework of the open-quotes Tilted Axis Crankingclose quotes model is suitable. This discussion will also contain comparisons with particle-rotor and open-quotes Principal Axis Crankingclose quotes model predictions

[en] Low-Ω members of three subshells dominate the level schemes in prolate Au nuclei (N = 100 - 106): the positive parity i_13/2 subshell, and the negative parity h_9/2 and f_7/2 subsbells. Because the latter are in near proximity and have similar deformation, bands built on h_9/2 and f_7/2 single-particle states are mixed. A detailed study of this mixing, however, has not been possible because of the lack of sufficient experimental data. In ¹⁸¹Au, four rotational bands have been identified with the h_9/2 and f_7/2 configurations. These data, along with data on other Au nuclei (including data from recently observed ¹⁷⁹Au), provide a new opportunity to study the h_9/2- f_7/2 mixing process. Experimental systematics will be compared with model calculations

[en] High spin states of the nucleus ¹⁸⁷Tl were populated with the ¹⁵⁶Gd(³⁵Cl,4n) reaction at 172 MeV. The measurement was performed at ATLAS using 12 Compton suppressed Ge detectors and a 50 element BGO ball. Several level structures have been established from the γ-γ coincidence analysis. The strongest one is a relatively low-lying (around 1 MeV) prolate rotational band observed up to spin 45/2. The configuration of this band will be discussed on the basis of comparisons with bandhead calculations and TRS calculations. A systematic comparison including band structures in A < 190 Tl isotopes and their respective Hg core nuclei will be presented

[en] Spectroscopic studies of weakly populated proton i_13/2 bands in superdeformed Tl nuclei (around mass 190) and in the normally deformed, very light ¹⁸³T1 nucleus are discussed. Among the results presented, the first measurement of a superdeformed quadrupole moment in an odd-Z nucleus, ¹⁹¹T1, is reported. The experiments were conducted with the Gammasphere array as ''stand-alone'' device and coupled with the Argonne Fragment Mass Analyzer. (author)

[en] High spin states of the ¹⁹²Tl were populated with the ¹⁶⁰Gd ³⁷Cl,5n reaction at 181 MeV. The experiment was performed at the Lawrence Berkeley Laboratory using the Gammasphere detector array with 34 counters (Early Implementation) to measure the in-beam γ rays. One purpose of this experiment was to study the superdeformed bands of ¹⁹²Tl in detail. A second purpose was the study of shape coexistence in the first well of the nucleus. At present, the analysis of the data has yielded the previously known band structures assigned as πh _9/2 vi₁₃₁₂ at oblate deformation. On top of the original level structure, many new transitions have been placed, which extend this structure through the back bending region. A new band structure consisting of two signatures has been established, and this band exhibits rotational character as well. The rotational alignment and the signature splitting in both bands will be discussed and compared with the similar level structures in A > 190 Tl isotopes and their respective Hg core nuclei

[en] Several groups from the University of Notre Dame are playing an important role in developing the research program at ATLAS. One of their main interests is the study, in collaboration with ANL staff members, of the behavior of nuclei at high spin in the transitional region near A=180 (i.e. the Hg-Pt-Os nuclei), and A=100 (i.e. the Ru-Tc nuclei) with emphasis on shape coexistence and configuration mixing. This group has also participated in many other experiments performed with the BGO gamma-ray facility, especially in the investigation of superdeformation. The γ-ray groups at ANL and Notre Dame have also had collaborative experiments at Gammasphere. The Notre Dame group has built, tested and extensively used a state-of-the-art plunger device for lifetime measurements in conjunction with the ATLAS γ-ray facility. An adapted version of this device is now under construction at Notre Dame, under contract with ANL, for use at the Gammasphere facility

[en] The effects introduced by 4π charged-particle detector arrays such as the Microball on lifetime measurements by Doppler-shift attenuation techniques are discussed. The effect originates from the lower efficiency for detecting charged particles at backward angles. Procedures for correcting for such 'bias' are described

No abstract available

[en] Ten band structures are observed in ¹⁶⁴Tm, among them sets of parallel and anti-parallel couplings of the proton and neutron spins. The Tilted Axis Cranking scheme is applied for the first time to an odd-odd nucleus in a prominent region of nuclear deformation