K. H. Maier

E2 moments andg-factors in neutron deficient lead isotopes

The half-lives of the (vi13/2)2Iπ=12+ isomers in190, 192pb were measured asT1/2 =7.9(4) μs and 1.10(5) μs, respectively. The quadrupole moment and theg-factor of the corresponding state in194Pb were determined toQ=49(3) efm2 andg=−0.167(2) using the perturbed angular distribution method. Additionalg-factor and lifetime information was obtained for a number of isomers in194, 195, 196, 197, 198, 199, 200Pb also involvingi13/2 neutrons. The results are discussed in comparison to a two-quasiparticle Tamm-Dancoff calculation in the full shell using the surface delta interaction.

γ-Spectroscopy of 89 215 Ac126 and proton pairing inN=126 isotones

Theγ-decay of 5 excited states along the yrast line has been observed in215Ac by inbeamγ-spectroscopy. Lifetimes andg-factors of 3 isomeric levels have been measured. The data show that pairing dominates the structure ofN=126 isotones.

In-beam spectroscopy of exotic nuclei with OSIRIS and beyond

Abstract The experimental techniques and recent results of nuclear structure studies in-beam close to 100Sn are reviewed. The structure of the nuclides 97Ag, 100Cd and 104Sn, so far the nuclei of closest approach to 100Sn with known excited states, is discussed within the spherical shell model. The basic shell model parameters of 100Sn, single particle binding energies and two-body matrix elements, as deduced from the shell model analysis, are summarized. From the available structure information conclusions are drawn for the design and expected phenomena of future experiments towards the far-from-stability doubly magic 100Sn.

In-beam spectroscopy of104Sn

The very neutron deficient nucleus 104Sn has been identified in in-beam spectroscopy using the reaction50Cr(58Ni, 2p2n) and neutron and charged particle multiplicity filter detectors. Excited states up to I ≈ 10 and Ex=4 MeV were observed and the level scheme is discussed in the frame work of the spherical shell model.

On the origin of the 2485 keV?-ray observed in near-barrier collisions of various heavy ions with208Pb

In collisions of64Ni and82Se projectiles with a thick208Pb target at energies around 10% above the static Coulomb barrier a 2485 keV Y-ray is observed, which is in conspicuous agreement with the recently reported Y-ray deexciting the two-phonon octupole state in208Pb [1]. The y-ray observed in the present experiments is not in coincidence with any known208Pb y-rays, but belongs likely to207Pb.

Nuclear structure study of the neutron deficient cadmium isotopes100, 101, 102Cd

The neutron-deficient nuclei100,101Cd were identified for the first time in — beam following the reactions58Ni +46,48Ti and58Ni +50Cr at 230 MeV and 245 MeV bombarding energy of the58Ni beams. Theγ-decay of the isotopes100,101,102Cd was studied inpγ, ppγ,nγ, nnγ, andnγγ prompt and delayed coincidence spectra. Isomers were found with spin and half life {ie1-01}=8+, T1/2=52(5) ns in100Cd, {ie1-02}=(19/2+), T1/2=4.6(4) ns in101Cd and {ie1-03}=8+, T1/2=56(4) ns in102Cd. In a PAD experiment theg-factor of the {ie1-04}=8+ isomer in100Cd was measured to be g=1.24(6). Using the reaction36Ar +70Ge at 135 MeV energy of the36Ar beam, theg-factor and the quadrupole moment of the {ie1-05}=8+ isomer in102Cd were measured to be g=1.29(3) and Q=87(10) fm2, respectively. The spectroscopic results are discussed within a shell model approach using a100Sn core, which accounts well for the electromagnetic properties of the proton aligned isomers. The structure of the spherical neutron states, dominated by the close lying vd5/2, g7/2 orbitals, and the gradually developing quadrupole collectivity are reproduced by the shell model calculations.

γ-decay of the particle-hole states with the highest spins in208Pb

Abstract208Pb has been excited with inelastic heavy ion scattering of 350 MeV64Ni and 420 MeV82Se on a thick208Pb target. Withγ -γ coincidence measurements 2 new decays of the 10+ isomer, namely a 34.5 keVE2-transition to 82+ and a 857.7 keVE3 transition to 7− have been found and the wavefunctions of the participating levels deduced. An observed gamma cascade of 295.3, 348.0, 865.4 and 340.2 keV on top of the 10+ isomer is assigned to the particle-hole states with the highest spins 14− 6744.1 keV→13− 6448.9 keV→12+ 6100.9 keV→11+ 5235.6 keV→10+ 4895.4 keV.

Identification and in-beam spectroscopy of the neutron deficient nuclei103In and105Sn

The neutron deficient nuclei103In and105Sn, neighbours of the drip line nucleus104Sn, have been identified by in-beam spectroscopy following the reaction58Ni + 50Cr at 250 MeV. Neutron and charged particle multiplicity filter detectors were used, and levels up to I ≈ 25/2 and Ex=4 and 6 MeV excitation energy were established in103In and105Sn, respectively. The experimental level schemes, so far with only tentative spin assignments, are compared to shell model predictions.

Shell model yrast states in the many-particle nucleus 72 157 Hf85

In-beamγγ- andγγn-measurements have for the first time identified excited states in the72157Hf85 nucleus and have established its yrast levels up to 6.5 MeV and I=(51/2). The results of parameter-free 11-particle recoupling calculations in the framework of the shell model for the configurationsπh112/8νf72/3 andπh112/8νf72/2h9/2 are in excellent agreement with the observed levels up to 39/2 at 4.758 MeV. A weakly populated 52 ns 29/2+ yrast isomer at 2.876 MeV is assigned as the three-neutron configurationνf7/2h9/2i13/2.

Nuclear Structure Close to 100Sn:Excitations of the Shell Model Core

The main topics of experimental β-decay and in-beam studies in the 100Sn region are the shell model structure [1–5], the residual interaction [6–9] and spin response phenomena as the quenching of Ml [3,10] and Gamow-Teller strengths [11]. Shell model calculations [3,6–9,12] in a small configuration space are generally in good qualitative agreement with the experiment. There are, however, a few unsolved problems, like e.g. the failure to reproduce the 94Ru and 95Rh B(E2)-values in the middle of the πg9/2 shell [1,6] or the spin gap isomerism in 95Pd [5]. Whether this is due to an inadequate residual interaction and/or configuration space can be studied best as close as possible to 100Sn.