J. Leske

Robust test of E(5) symmetry in 128Xe

Low-lying collectively excited states of 128 Xe were investigated by γ-ray spectroscopy following the 12 C( 128 Xe, 128 Xe*) 12 C projectile Coulomb excitation reaction. Nineteen absolute E2 transition strengths were obtained including the first measurement of the critical B(E2) decays from the second and third J π = 0 + states. These data are compared with the theoretical predictions of the critical point symmetry E(5) and allow us to conclude that 128 Xe is not an E(5) nucleus as previously suggested, leaving 130 Xe as the most likely candidate among the Xe isotopes.

Exotic ideas on mixed proton-neutron symmetry and their manifestation in heavy nuclei

The one-quadrupole phonon excitation of mixed symmetry, the 2+1,ms state, is a fundamental building block of nuclear structure. This article gives a summary of our recent experimental research on this excitation mode in the A = 90 and A = 130 mass regions.

The beauty of good data: Unveiling the traces of mixed symmetry

The one-quadrupole phonon excitation of mixed symmetry, the 2+1,ms state, is a fundamental building block of nuclear structure. This article gives a summary of our recent experimental research on this excitation mode in the A = 90 and A = 130 mass regions.

New lifetime measurements in the stable semimagic Sn isotopes using the Doppler-shift attenuation technique

Precise measurements of lifetimes in the picosecond range of excited states in the stable even-A Sn isotopes 112,114,116,122Sn have been performed using the Doppler shift attenuation technique. For the first excited 2+ states in 112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously adopted values. They indicate a shallow minimum at N = 66 in contrast to the maximum at mid-shell predicted by modern shell model calculations.

New measurement of the {sup 68}Zn(4{sub 1}{sup +}) g factor combined with a reanalysis of previous data

We have remeasured and have redetermined the g factor for the 4{sub 1}{sup +} state in {sup 68}Zn following inconsistencies between earlier measurements and a recent result. We have reanalyzed several former measurements by applying an alternative analysis procedure, which allows for determining the precession effect separately for each gamma detector implying less uncertainties in the background subtraction for the relevant spectra. In addition, all measured g-factor and B(E2) data for the first 2{sup +} and 4{sup +} states in all stable even-A Zn isotopes and the radioactive {sup 62}Zn, are compared with new large-scale shell model calculations based on the most advanced effective interaction in the fpg-shell model space.

Polarization Sensitivity of the DAGATA Polarimeter

In comparison to common Compton Polarimeters the DAGATA (Darmstadt GAmma‐ray Tracking Assembly) polarimeter will significantly enhance the sensitivity for γ‐rays above 4 MeV making use of its large volume 36‐fold segmented HPGe AGATA crystal and the resulting superior position resolution. Results from Monte Carlo Simulations will be presented as well as approaches for data analysis to further improve the sensitivity. Application limits and realistic simulated spectra will be compared to results from existing polarimeters.

Robust test of E(5) symmetry in {sup 128}Xe.

Low-lying collectively excited states of 128 Xe were investigated by γ-ray spectroscopy following the 12 C( 128 Xe, 128 Xe*) 12 C projectile Coulomb excitation reaction. Nineteen absolute E2 transition strengths were obtained including the first measurement of the critical B(E2) decays from the second and third J π = 0 + states. These data are compared with the theoretical predictions of the critical point symmetry E(5) and allow us to conclude that 128 Xe is not an E(5) nucleus as previously suggested, leaving 130 Xe as the most likely candidate among the Xe isotopes.

Probing High‐Velocity Transient‐Field Strength Using Heavy‐ions Traversing Fe and Gd

The transient field strength for 76Ge ions, passing through iron and gadolinium layers at velocities ∼Zv0, has been measured. Although a sizeable value has been obtained for Gd, a vanishing strength has been observed in Fe.

Isovector quadrupole excitations in the valence shell of vibrational nuclei

Coulomb excitation experiments in inverse kinematics of stable ions impinging on a carbon target at energies of about 85% of the respective Coulomb barriers have been performed in the A∼130 region. Proton‐neutron mixed‐symmetry one‐quadrupole phonon state 21,ms+ has been identified in several nuclides from the large B(M1;21,ms+→21+) value as compared to typical M1 strengths between low‐energy 2+ states. As an example, we focuss on the evolution of the 21,ms+ state in the N = 80 isotonic chain. The local proton‐neutron quadrupole‐quadrupole interaction strength is determined from these data within a schematic two‐state mixing model.