H. Kluge

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.

Shell model structure at100Sn — The nuclides98Ag,103In, and104, 105Sn

The neutron deficient nuclei98Ag,104Sn withTz=2 and103In,105Sn (Tz=5/2) were studied in-beam following the reaction of 250 MeV58Ni+50Cr. Neutron and charged particle (p, α) gatedγγ-coincidence spectra were used to identify these nuclei, which are populated with yields between 0.05% and 2% of the total residue cross section, and to determine their level schemes. In a comprehensive shell model study various approaches for the residual interaction were used to describe these newly and several previously studied neutron deficient nuclei. As a result predictions for the neutron single particle energies for100Sn are obtained and used to discuss the next generation of experiments.

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.

High-spin states in109Sn and their decay to the ground state

An extended level scheme of109Sn is presented showing high-spin states up to Ex≈ 8 MeV and spins up toJπ=(41/2+). Their decay to the 5/2+ ground state has been observed identifying a 12.8 keV 7/2+ → 5/2+ transition. A half-life of T1/2=7(1) ns has been measured for the 17/2+ state atEx=2114 keV. The experimental data are compared with the predictions of shell-model calculations.

Spectroscopy of198,199Po

Excited states in198,199Po have been studied by in-beamγ-ray spectroscopy. These nuclei were produced in the 4n and 5n reaction channels for 115 MeV20Ne on183W-targets. Multipolarities and mixing ratios ofγ-transitions were determined from DCO-ratios, leading to spin/parity assignments. In198Po,γ-cascades have been observed above several excited levels that are similar to the vibration-like structure built on the ground state. In199Po, the coupling of the oddi13/2 neutron seems to favor the spherical shape of the even core; no levels resembling the intruder states of the even nuclei are found. A semi-quantitative evaluation of the cross-sections for nuclei produced in fission and multi-particle transfer is presented.

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.