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The nuclear electric quadrupole moments of the isotopes 26 Na, 27 Na, 28 Na and 29 Na were measured by -NMR spectroscopy in single crystals of LiNbO 3 and NaNO 3 . High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear laser beam. The polarized nuclei were implanted into the crystals and NMR signals were observed in the -decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of 27,31 Na and con rmed the spin I = 3=2 for 31 Na. The results are discussed in comparison with large-basis shell-model calculations.

We report on the measurement of optical isotope shifts for 32 40 Ar and for 46 Ar from which the changes in mean square nuclear charge radii across the N = 20 neutron shell closure are deduced. The investigations were carried out by collinear laser spectroscopy in fast beams of neutral argon atoms. The ultra-sensitive detection combines optical pumping, stateselective collisional ionization and counting of -radioactivity. By reaching far into the sd-shell, the results add new information to the systematics of radii in the calcium region (Z 20). Contrary to all major neutron shell closures with N 28, the N = 20 shell closure causes no signicant slope change in the development of the radii. Information from the hyperne structure of the odd-A isotopes includes the magnetic moments of 33 Ar (I = 1 = 2) and 39 Ar (I = 7 = 2), and the quadrupole moments of 35 Ar, 37 Ar (I = 3 = 2) and 39 Ar. The electromagnetic moments are compared to shell-model predictions for the sd-and fp-shell. Even far from stability a v ery good agreement between experiment and theory is found for these quantities. The mean square charge radii are discussed in the framework of spherical SGII Skyrme-type Hartree-Fock calculations.Keywords: NUCLEAR STRUCTURE 32 40;46 Ar; measured isotope shifts, hfs; deduced hyperne constants, spins I, magnetic dipole moments , electric quadrupole moments Q s , mean square charge radii hr 2 i; Collinear fast-beam laser spectroscopy, collisional ionization and -detection; shell model (sd-, fp-shell).

A β-decay study of the even mass 74,76,78 Cu isotopes toward levels in 74,76,78 Zn was performed at the ISOLDE mass separator. The copper isotopes were produced in proton-or neutron-induced fission reactions on 238 U, laser ionized, mass separated, and sent to a β-γ detection system. Half-lives, decay schemes, and possible spin configurations were obtained for the copper isotopes. The results are compared with calculations using schematic forces as well as large-scale shell-model calculations with realistic forces.

The ISOLDE resonance ionization laser ion source (RILIS) allows to ionize efficiently and selectively many metallic elements. In recent yield surveys and online experiments with the ISOLDE RILIS we observed 23 (Submitted to Nuclear Instruments and Methods in Physics Research B) IntroductionThe resonance ionization laser ion source (RILIS) [1] provides an efficient, fast and selective way to ionize many metallic elements. The elements ionized with the ISOLDE RILIS were reviewed recently [2,3,4]. In this article we will discuss on-line results, i.e. release curves and yields measured in recent target tests, nuclear spectroscopy experiments and on-line collections.The measured release curves were fitted with the empiric 4-parameter-formula described in [5,6]. Table 1 shows a summary of the release parameters: t r the rise time, t f the fall time of the fast component, t s the fall time of the slow component and α the relative intensity of the fast component. Parameters which had to be fixed to obtain a stable fit are marked in parentheses.The release parameters were used to determine for each radio-isotope the fraction which is released before it decays. The on-line efficiency of the RILIS cannot be easily monitored as in the case of a plasma ion source where the support gas is injected at a well-defined flowrate. Still a rough estimate can be made by scaling the off-line measured efficiency with the laser power available in the on-line run. Also the ion yield of a longlived isotope with known production cross-section gives an indication of the ionization efficiency. Correcting the ion yields for the released fraction and the ionization efficiency allows to deduce the in-target production yield. In some of the following graphs both values are plotted: the ion yield, showing the presently available radioactive ion beam intensity for the user, and the in-target production yield showing the theoretical limit that could be obtained with an ideal target (no decay losses) of the same thickness and dimensions coupled to an ideal ion source (100 % efficiency). The ratio between both curves shows the overall efficiency of the present target and ion source unit.

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We have obtained information on the atomic hyperfine splitting and, hence, on magnetic moments in neutron-rich 68,70 Cu isotopes by scanning the frequency of the narrow-band laser of the first excitation step in the resonance ionization laser ion source. The method of in-source atomic spectroscopy, as well as the analysis of the obtained data, is described. The results are discussed in terms of single-particle configurations coupled to the 68 Ni core.

Recently isotope shifts of 72, Kr and 77-100 Sr have been measured at the ISOLDE/ CERN mass separator facility by collinear laser spectroscopy. The deduced changes in mean square charge radii reveal sharp transitions in nuclear shape from spherical near the magic neutron number N=50 towards strongly deformed for both the neutron deficient and neutron rich isotopes far from stability. The mean square charge radii of the neutron deficient isotopes exhibit a sign change of the odd-even staggering (OES), i.e. below the neutron number N=46 the radius is systematically larger for the odd-N nuclei than for their even-N neighbours. This is in contrast to the situation of normal OES which is observed for the heavier isotopes. The inversion of the OES is interpreted as an effect of polarization, triggered by the addition of an unpaired neutron and driving the soft eveneven core into stable strong deformation. accepted for publication in Europhysics Letters (IS80 and IS304)