[en] The paper reports on the Level Mixing Resonance experiment performed on the β-decaying ¹⁸N nucleus produced and aligned in an intermediate-energy fragmentation reaction. From the resonantly induced change in an asymmetry of the β-decay, measured as a function of a static magnetic field, the authors derived information on the nuclear moments of the neutron-rich ¹⁸N nucleus. The spectroscopy quadrupole moment (Q(¹⁸N,I^-))=3.2(3)e fm² is compared to mean-field calculations

[en] Results from a pioneering experiment to measure the g factors of isomeric states of neutron-rich nuclei around ⁶⁸Ni, far from the valley of β stability are reported. For the first time the time-dependent perturbed angular distribution method was applied in combination with the heavy-ion-γ correlation technique to study g factors of spin-aligned isomers produced in a projectile fragmentation reaction and mass-separated. Some technical aspects are discussed and illustrated with preliminary results

[en] We present the first Level Mixing Resonance measurements performed on radioactive nuclei produced in intermediate energy fragmentation reactions and mass separated with the SPEG and LISE3 mass spectrometers at the Grand Accelerateur National d'Ions Lourds (GANIL, Caen, France). The β-anisotropy of initially aligned secondary fragments was measured as a function of an externally applied magnetic field. The amplitude of the measured resonance is proportional to the alignment of the projectile fragments, and its position is proportional to the ratio of the static quadrupole moment to the magnetic moment of the selected nuclei. The alignment of ¹² B and ¹⁸ N fragments has been determined for different cuts in their longitudinal momentum distribution and is ranging from 0.9% to 14.4%. The ratio of the quadrupole frequency to the magnetic moment for ¹⁸ N is found to be a factor of 10 larger than for ¹² N. (author)

[en] Using the Level Mixing Resonance (LMR) interaction, which converts alignment into polarization, the nuclear spin alignment of ¹²B produced in two different fragmentation reactions at intermediate energy (respectively ¹³C onto a ¹²C target and ²²Ne onto a ⁹Be target) was determined by measuring the β-anisotropy. The nuclear spin alignment of ¹⁸N fragments, produced in the ²²Ne reaction was measured for different selections in the longitudinal fragment momentum distribution. In the same measurement the ratio of the quadrupole frequency to the magnetic moment ν_Q/μof neutron rich ¹⁸N fragments implanted in Mg was found to be an order of magnitude larger compared to simple shell model calculations. (author)

[en] The ratio of the quadrupole moment of the 8⁺ isomers in ²⁰²Po and ²⁰⁴Po has been measured in a Pt host using the level mixing spectroscopy method: Q(²⁰²Po)/Q(²⁰⁴Po)=1.06(13). The increase of the Po(8⁺) quadrupole moments with decreasing neutron number can be explained by explicitly taking into account the interaction between the vertical stroke π1h²_9/2 right angle two-proton configuration and the core quadrupole vibrational excitations of the underlying even-even Pb core. A very good quantitative agreement is observed, indicating that core polarization near the Z=82, N=126 closed-shell region can be understood by particle-core coupling. (orig.)

[en] An extension of the time-integrated atomic decoupling technique to measure g-factors of (sub)nanosecond isomers and/or the magnetic hyperfine field induced by highly excited atomic electrons on nuclei recoiling into vacuum is discussed. A high average field B_hf=1080_-175⁺²⁷⁰ T and an average atomic spin J=2.7(2) is deduced using the known magnetic moment of a 4.05(7) μs isomer in ⁶⁹Ge. Such high magnetic fields allow g-factor measurements of (sub)nanosecond states. Ab initio calculations show that the combination of a high average magnetic hyperfine field and a high average atomic spin is only possible if a considerable fraction of the ions is in a metastable excited state

No abstract available

[en] An overview of some recent results on nuclear moment measurements on isomers is being given. Neutron rich isomers have been produced in a fragmentation reaction at GANIL. Using the spin-orientation of the fragment beam, isomeric g-factors around ⁶⁸Ni have been measured by detecting the Larmor precession via the isomeric γ-decay (TDPAD-method). Isomers in the mass A∼180 region were produced in a fusion-evaporation reaction at Louvain-la-Neuve. The quadrupole moment of a 5 quasi-particle isomer in the deformed nucleus ¹⁷⁹W was measured using the Level Mixing Spectroscopy (LEMS) method. Both results show how details on the nuclear structure can be investigated via nuclear moment measurements. (author)

[en] The Level Mixing Spectroscopy (LEMS) method has proven to be a powerful method to determine the quadrupole moment of high spin isomers. There are some limitations on the use of the method which are due to the fact that a non cubic host providing an electric field gradient and a large superconducting magnet are needed. In this contribution we report on the use of cubic host materials as a first expansion of the applicability of the LEMS method towards a wider region on the nuclear chart. In two experiments we have shown that a defect-associated electric field gradient, induced by the nuclear reaction in a cubic host material, is reproducible and can be used to determine quadrupole moments. We also discuss how the use of magnetic host materials cancels the need for a superconducting magnet by taking advantage of the very strong, temperature dependent hyperfine fields near the Curie temperature. (author)

[en] The Level Mixing Resonance (LMR) technique allows to determine ground-state nuclear moments by measuring the spin-polarization of the beta-decay, and starting from an initially aligned ensemble of nuclei. Using this new technique, the ratio of the quadrupole frequency to the magnetic moment of the neutron rich ¹⁸N ground state has been measured: ν_Q/ν(¹⁸NMg/) = 1328(33) kHz/n.m. In order to measure the nuclear moments independently, the Nuclear Magnetic Resonance (NMR) and LMR techniques will be combined. (author)