[en] Two nuclear hyperfine levels can cross when a quadrupole and magnetic interaction are combined. When the levels come close enough, interferences between two transitions can occur if coherence conditions are fulfilled. In this paper we discuss the possibility that coherence and interferences could occur if the zero fluctuations of an electromagnetic field in a crystal lattice would be anisotropic

[en] Some features of quantum optics related to inversionless amplification are translated to nuclear systems. Nuclei and nuclear transitions differ in several ways from atomic systems: gamma radiation has a much shorter wavelength (of the order of lattice-distances), nuclear transitions are many orders of magnitude weaker than atomic ones (making nuclear pumping extremely hard), no coherent gamma-ray sources are available to produce bichromatic gamma radiation. All this makes it very hard to merely translate quantum optical results to nuclear systems. We show that under very specific conditions destructive quantum interferences can occur in the nuclear absorption probability, while the stimulated emission probability is not affected. Nuclear level mixing plays a crucial role in this

[en] Collinear laser spectroscopy is a very powerful tool to study the spin, electromagnetic moments and charge radii of exotic isotopes in a model-independent way. At ISOLDE-CERN two collinear laser beam lines are currently operational, one dedicated to the optical detection of hyperfine structures from resonantly excited atoms or ions (COLLAPS) and one dedicated to Collinear Resonance Ionization Spectroscopy (CRIS) with ion detection. In this presentation I will explain the complementarities of both techniques and address some recent scientific highlights, with a focus on the study of shape changes (with possible examples on Mn, Cu, Zn, Cd and Fr isotopes). This document is composed of an abstract and the slides of the presentation. (author)

[en] We present systematic calculations of the properties of 11^- isomers in neutron-deficient ^184-198Pb and ^188-200Po. These states are based on the π(h_9/2i_13/2)_K^π=11^- configuration. They are calculated in the framework of the Hartree-Fock-Bogoliubov method with a Skyrme interaction and density-dependent pairing force. The energies and deformations of the 11^- states are compared to those of the intruder 0⁺ states in both Pb and Po isotopes. In the most neutron-deficient Po isotopes, the calculations predict, below a weakly oblate 11^- state, another oblate 11^- state which is even more deformed than the intruder oblate 11^- state in their Pb isotones. The energies and quadrupole moments of the 11^- isomers, corresponding to a weakly oblate nuclear shape, are in fair agreement with the available experimental data

[en] A time integral method for the study of resonant nuclear scattering of synchrotron radiation in the forward direction is presented. The method relies on the interference of radiation scattered by nuclei in two samples, one moving with respect to the other. The method, termed heterodyne detection of synchrotron radiation, gives the same information on hyperfine parameters as the well known differential method. The general formalism is developed for the case where the reference is a single line sample and the investigated sample has magnetic or quadrupole splitting. The first experiments are discussed. A comparison of time differential synchrotron radiation spectroscopy, heterodyne detection and Moessbauer spectroscopy is given

No abstract available

[en] Two types of decoupling experiments are described: Decoupling of the quadrupole interaction of an isomer in a non-cubic host and decoupling of the electron-nucleus interaction of a recoiling free atom in vacuum or gases. Both perturbation interactions can be decoupled from the nuclear system by applying a large magnetic field. Some examples and results of both types of experiments are given. (orig.)

[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] This paper intends to introduce the reader into Level Mixing Spectroscopy (LEMS), and to the results obtained with it so far. LEMS is a rather recent method used to study the quadrupole interaction of isomeric states in solid hosts, and was developed at Leuven. After an introduction dealing with both the theoretical background and the experimental set-up, a detailed comparison will be made with the Time Differential Perturbed Angular Distribution (TDPAD) - method. It turns out that LEMS is well suited for very high spin states in the ns-ms lifetime region. In the second part, the results in isotopes of Bismuth (10^--isomers in ^202-204-206Bi and the 21/2⁺-state in ²⁰⁷Bi), Astatine (²¹¹At, 29/2⁺ - and 39/2^--states; ²¹⁰At, 15^- - and 19⁺-isomers; ²⁰⁹At, 29/2⁺-isomer and ²⁰⁸At, 16^--level) and Francium (²¹³Fr, 29/2⁺ - and 65/2^--levels; ²¹²Fr, 15^-- and 27^--states and ²¹¹Fr, 29/2⁺- and 45/2^--isomers) are discussed. The spin values range from 10 up to 65/2 and the lifetime region extends from 70 ns up to 13 ms, which proves already the applicability of LEMS. The results will also be compared to other data known so far in the ²⁰⁸Pb-region. (orig.)

[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)