E. F. Zganjar

New neutron-rich 179Yb and 181,182Lu isotopes produced in reactions of 9 MeV/u 136Xe ions on tantalum and tungsten targets

Abstract The new neutron-rich isotopes 179 Yb and 181,182 Lu were produced in multinucleon transfer reactions by irradiating nat W/Ta targets with 9 MeV/u 136 Xe ions, and identified by mass separation and decay spectroscopy. The measured half-lives of 179 Yb, 181 Lu and 182 Lu are 8.1±0.8, 3.5±0.3 and 2.0±0.2 min, respectively. The properties of the excited states of 181,182 Hf are discussed. The possibility of studying neutron-rich nuclei outside the classical fission-product regions is demonstrated.

Rotation-aligned coupling and axial asymmetry in 189−195Au

Abstract Levels in 189, 191, 193Au have been studied by radioactive decay of isotopically separated 189, 191, 193Hg. The systematics of the levels are followed from 195Au to 189Au and show a remarkable insensitivity to neutron number. The h 1 1 2 bands are identified and provide a critical test of the model of a single-j nucleon subject to rotation-aligned coupling to an asymmetric core. Within the framework of the model the triaxial degree of freedom appears to be very stable.

The decay of 110mAg: Gamma-ray energy and intensity standardization

Abstract The energies and intensities of the transitions from the decay of 110mAg have been carefully measured with three different systems which use Ge(Li) detectors. The following energies in keV and intensities in parentheses were determined for standards: 446.77 ± 0.04 (3.5 ± 0.2), 620.22 ± 0.03 (2.9 ± 0.2), 657.71 ± 0.03 (100), 677.55 ± 0.03 (12.2 ± 0.7), 686.80 ± 0.03 (7.4 ± 0.6), 706.68 ± 0.04 (17.2 ± 07), 744.19 ± 0.04 (4.4 ± 0.4), 763.88 ± 0.04 (24.0 ± 0.8), 818.00 ± 0.04 (7.8 ± 0.3), 884.67 ± 0.04 (79.6 ± 2.0). 937.48 ± 0.04 (36.5 ± 1.1), 1384.22 ± 0.04 (27.7 ± 0.8) 1475.73 ± 0.04 (4.5 ± 0.2), 1504.90 ± 0.08 (14.8 ±0.4) and 1562.22 ± 0.06 (1.33 ± 0.06). All these transitions fit into the well-known decay scheme of 110mAg. Transitions previously reported at 566.0, 667.2, 753.0, 785.0 and 1443.0 keV were not observed, but weak new transitions at 626, 997 and 1334 keV were observed. Transitions of 434.00 ± 0.10, 614.37 ± 0.10 and 722.95 ± 0.08 keV were observed from the decay of 108mAg.

The structure of high spin states in 184Hg and 186Hg

Abstract The structure of 184 Hg has been studied through the 156 Gd( 32 S, 4n) reaction. The spins of the levels up to 18 + were established by measuring directional correlation ratios from oriented nuclei. Mean lifetimes of the levels from 8 + to 18 + were measured by the Doppler shift attenuation method. The deduced |β 2 | values are nearly constant to indicate a stable nuclear shape. The deformed band (up to tentative spin 24 + ) shows two upbendings at h ω ∼ 0.26 MeV and h ω ∼ 0.33 MeV . Cranked shell-model calculations suggest that these band-crossings can be associated with v i 13 2 and π h 9 2 pairs at prolate shape. A new interpretation of previously reported band structures in 186 Hg is given.

Precision gamma-ray spectroscopy on the decay of 168Tm

Abstract Precision gamma-ray energy and intensity measurements have been made on the decay of 87 d 168 Tm. The uncertainty in energy of the more prominent gamma rays ranged from 20 to 40 eV, and the uncertainty in the relative intensity varied from 1 to 5%. The available conversion electron intensity data were used with the data here to calculate internal conversion coefficients. A decay scheme consistent with these results is presented, and several ambiguities of the previous 168 Tm decay schemes have been resolved. The E2 branching ratios from the gamma vibrational band to the ground state band were calculated and, when compared to band-mixing theory, gave the following values for the vibration-rotation coupling parameter z 2 : 0.0278 ± 0.0055, 0.0284±0.0091, 0.0283±0.0056, 0.0314±0.0025 and 0.0329±0.0015. A weighted average of the values is 0.0320±0.0013.

Signature of the shape coexistence in 72Kr: discontinuities of the moment of inertia at low spin

Abstract The low-lying level structure of the N=Z nucleus 72Kr was studied by 40 Ca ( 35 Cl, p , 2 n γ) 72 Kr at 95 MeV. Gamma ray coincidences are used to construct for the first time a level scheme for this nucleus based on coincidence gating with the previously identified 2+−0+ transition. The new level scheme indicates strong prolate-oblate mixing of two shape coexisting bands. The results support theoretical predictions of a stable oblate minimum in this region.

The Gamow-Teller transitions in the96Pd→96Rh decay

Using the40Ca(4.2 MeV/u) +60Ni reaction and on-line mass separation, the decay properties of4696Pd50 were reinvestigated. From a comparison of experimental and theoreticalβ+/(EC +β+) probability ratios, theQEC value was deduced to be 3,450 ± 150 keV. The strength was determined for four 0+→1+ Gamow-Teller beta transitions and found to be quenched as compared to predictions of the single-particle shell model. For96Pd and94Ru the sources of this quenching are discussed.

The new beta-delayed proton precursors103Sn and105Sn

Using58Ni+50Cr and58Ni+54Fe reactions and on-line mass separation, the new isotopes103Sn and105Sn with half-lives of 7±3 s and 31±6 s, respectively, were identified via their beta-delayed proton decays. The relative yields and the possibility of reaching101Sn are discussed.

The mixing of the gamma vibrational and ground state bands in 160Dy

Abstract They γ-ray spectra accompanying the β − decay of 160 Tb to levels in 160 Dy has been studied using Ge(Li) detectors. Coincidence measurements were made in order to separate unresolved transitions. Five reduced E2 transition probability ratios for transitions between the gamma and ground state band were computed from the measured γ-ray energies and intensities. The band mixing parameters deduced from each ratio are determined to be mutually inconsistent. The values, z 2 × 10 3 , are: 49.5±4.0, 18.7±2.8, 29.24±2.1, 30.5±4.7 and 55.8±5.6. A critical inconsistency with internal conversion data is pointed out.

Contrasting behavior of h92 and i132 bands in 185Au

Abstract High-spin states in 185Au have been populated via the 169Tm(20Ne, 4nγ) and 175Lu(16O, 6nγ) reactions. We observe two aligned bands built on rapidly downsloping h 9 2 and i 13 2 proton orbitals. This permits one to examine for the first time the role of these and other orbitals in backbending, free from deformation effects. The i 13 2 band is observed to backbend, as does the 184Pt core, but the h 9 2 band does not, thus providing strong evidence for the dominant role of h 9 2 protons to backbending in this nucleus.