D. Borremans

Magnetic moment of the fragmentation-aligned 61Fe (9/2(+)) isomer.

We report on the g factor measurement of an isomer in the neutron-rich (61)(26)Fe (E(*)=861 keV and T(1/2)=239(5) ns). The isomer was produced and spin aligned via a projectile-fragmentation reaction at intermediate energy, the time dependent perturbed angular distribution method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the nuclear spin ensemble has been observed, allowing a precise determination of its g factor, including the sign: g=-0.229(2). In this way we open the possibility to study moments of very neutron-rich short-lived isomers, not accessible via other production and spin-orientation methods.

Quadrupole moments of the 11− intruder isomers in 194,196Pb in the particle-core coupling model

Abstract The recently measured spectroscopic quadrupole moments of the 11 − intruder isomers in 194,196 Pb are being discussed in the particle-core coupling model. The essential physics behind the nature of these isomers is revealed by a simple two-level-mixing calculation, showing that the coupling of the valence proton particles with vibrations of the underlying Hg core induces a factor of two increase of the quadrupole moments.

Quadrupole moment of the 8{sup +} yrast state in {sup 84}Kr

The quadrupole moment of the 8{sup +} yrast state in {sup 84}Kr was measured using the level-mixing spectroscopy technique to be Q= 36(4) e fm{sup 2}. The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8{sup +} states in Kr, Sr and Zr isotopes with N= 48, 50 and for 9/2{sup +} states in isotopes with N= 47, 49 suggests a modification of the effective charges used in this region.

Nuclear alignment in projectile fragmentation as a tool for moment measurements

The application of the Time Dependent Perturbed Angular Distribution (TDPAD) method to study isomeric states produced and oriented in projectile‐fragmentation reactions provides the opportunity to perform nuclear‐moment measurements in a wide range of neutron‐rich nuclei, unaccessible by other means. An absolute necessity for the application of the TDPAD technique is a spin‐aligned ensemble of nuclei. The preliminary results from a recent application of this method on 61mFe and 54mFe at GANIL, Caen, France showed that a significant increase of the amount of the observed alignment, compared to our previous measurement on 67mNi and 69mCu, can be obtained. Some experimental details, concerning the conservation of the reaction obtained alignment, are discussed.

Quadrupole moments of the 11− intruder isomers in 194,196Pb

The spectroscopic quadrupole moments of the 11− isomers in 194Pb and 196Pb have been measured by applying the Level Mixing Spectroscopy technique. These isomers have the π(s1/2−2h9/2i13/2) proton configuration. The implications of these results for the influence of the intruder character of the isomers on their deformation is given. We will especially focus on a simple 2-dimensional model, taking into account the coupling of the valence nucleons with the vibrations of the underlying core, which gives theoretical insight in the obtained experimental results for the quadrupole moments of the 11− isomers.