[en] Four superdeformed bands have been confirmed in ¹⁹²Tl. Two of these bands have I⁽²⁾ dynamic moments of inertia which are nearly constant with rotational frequency ℎω. The other two bands show the characteristic rise of I⁽²⁾ with increasing ℎω seen in most superdeformed bands of the A = 190 region of superdeformation. From comparisons with the odd-A neighbors, it was found that the alignments of these bands relative to a ¹⁹²Hg core can be accounted for from the additive contributions of the assigned quasiproton and quasineutron orbitals. copyright 1996 The American Physical Society

[en] States in the superdeformed (SD) well of the odd-odd nucleus ¹⁹²Tl have been studied via the ¹⁶⁰Gd(³⁷Cl,5n) reaction at 178 MeV. The experiment was performed using early implementation of Gammasphere in which three fold γ-ray coincidences were detected by 36 HPGe detectors. Four SD bands are clearly identified as belonging to the nucleus ¹⁹²Tl. Two of these bands exhibit nearly constant dynamic moments of inertia, π², as a function of average ℎω over the range 0.15 to 0.35 MeV. This result supports the earlier proposal that these open-quotes flatclose quotes bands correspond to quasiparticle configurations involving the occupation of the πi^13/2 and νj^15/2intruder orbitals, which would block both proton and neutron alignment. The other two observed SD bands each display an increasing π² as a function of frequency which is more typical of other SD bands in this region. The behavior of all bands along with the assignment of possible quasiparticle configurations will be discussed

[en] Superdeformation studies in ^189,191,192Tl at Gammasphere are discussed. New results on ¹⁹¹Tl are the observation of interband transitions between the signature partner E2 bands and the measurement of an average quadrupole moment (Q₀ = 18 ± 1 eb) for these superdeformed structures. These data enable them to derive absolute M1 strengths and confirm that the 81st proton occupies the [642]5/2 orbital. Tentative data for one superdeformed sequence in ¹⁸⁹Tl are consistent with the prediction of a decrease in quadrupole deformation for the lightest nuclei at the limit of this island of superdeformation

[en] Rotational bands associated with superdeformed (SD) shapes in A ∼ 190 mass region are identified by the dynamic moment of inertia, which rises smoothly with the rotational frequency (ħw). In the present approach, we have calculated band head MoI of SD bands available in "1"9"2Tl in A ∼ 190 mass region using soft rotor formula (SRF)

[en] Six superdeformed bands have been found in the nucleus ¹⁹²Tl. For two of the bands, the dynamic moment of inertia J⁽²⁾ is found to be constant with the rotational frequency ℎ. This result can be understood in terms of Pauli blocking of quasiparticle alignments in intruder orbitals, and represents the first experimental evidence that the alignment of these intruders is responsible for the smooth rise in J⁽²⁾ seen in other superdeformed nuclei of this mass region

[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] The particle-number conserving (PNC) method for treating the cranked shell model with monopole and quadrupole pairing correlations is used to study the superdeformed (SD) bands observed in odd-odd nuclei in the A∼190 mass region. Spins are assigned to the levels in these bands. The microscopic mechanism of the -bar ω evolution of the dynamic moment of inertia J⁽²⁾ for these SD bands are analyzed. In particular, the major roles of the j_15/2 neutron and i_13/2 proton orbitals played in the SD bands are investigated in detail by contributions to J⁽²⁾ from each cranked orbital and interference terms between two cranked orbitals. Additivity in the A∼190 mass region is investigated. The experimental evidence for additivity of alignments in ¹⁹²Tl can be reproduced by our calculations

[en] The TDPAD technique has been used to measure the electric quadrupole coupling constants for the ₁₉₂Tl(8^-) isomer in hexagonal Tl at different temperatures and in tetragonal In at room temperature. The values measured were e₂qQ/h = 24.0(15) MHz extrapolated to T = 0 K, and 33.1(16) MHz at 293 K for the Tl and In hosts, respectively. The electric field gradient for Tl impurities in In was determined from systematics of isoelectric systems, yielding /Q[₁₉₂Tl(8^-)1]/ = 0.44(7) b. The almost perfect symmetry of the Tl crystalline structure makes this metal a sensitive probe to current models for electric field gradients in metals. The magnitude and temperature dependence of the field gradient in thallium metal are discussed within the framework of such models. (author)

[en] The results of experiments on rotational bands in light Tl nuclei are used to indicate the richness of shape phenomena in the vicinity of a closed proton shell. Rotational bands associated with normal prolate and oblate shapes as well as with a superdeformed shape are observed. 34 refs., 4 figs

[en] The study of yrast and near-yrast structures of odd-odd nuclei to high spins is somewhat limited due to the complexity of the spectra resulting from the many proton-neutron couplings near the Fermi surface. In superdeformed nuclei, the number of available protons and neutrons near the Fermi surface is somewhat limited due to the presence of large-shell gaps which stabilize the nuclear shape. A relatively small number of available neutron and proton configurations can lead to fragmentation of the SD intensity into a number of different bands. Two good examples of this phenomenon were found in ¹⁹²Tl and ¹⁹⁴Tl where the presence of six superdeformed bands were reported in both nuclei. We reexamined ¹⁹²Tl at Gammasphere using the ¹⁶⁰Gd(³⁷Cl,5n) reaction at 178 MeV to populate states in the superdeformed well of this nucleus. While our previous study on ¹⁹²Tl at ATLAS was very successful, a number of questions remained which formed the basis of our objectives in this experiment: obtain better γ-ray energies for the known transitions and identify higher spin members in each band; determine how the bands feed the known yrast states in ¹⁹²Tl as well as determine the complete spectrum in coincidence with the SD bands; look for M1 transitions connecting proposed signature partners; and attempt to identify other excitations in the superdeformed well. Analysis is underway and four of the six bands were confirmed. The reasons that two of the reported bands were not observed in this latest work is still under investigation. As of this time, no other superdeformed bands were identified in the data. Two of the confirmed SD bands have a constant moment of inertia and show indications of cross-talk between each other. This observation is not unexpected since the calculated M1 rates for the proposed configuration of the band, π_13/2 x υj_15/2, indicate that M1 transitions linking the two SD bands should be observed