The isotopes 68 74 Ni, of interest both for nuclear physics and astrophysics, have been produced in proton-induced fission of 238 U and ionized in a laser ion guide coupled to an on-line mass separator. Their b decay was studied by means of b-g and g-g spectroscopy. Half-lives have been determined and production cross sections extracted. A partial level scheme is presented for 73 Cu and additional levels for 71 Cu, providing evidence for a sharply lowered position of the p1f 5͞2 orbital as occupancy of the n1g 9͞2 state increases. The latter may have a clear impact on the predicted structure and decay properties of doubly magic 78 Ni. [S0031-9007 (98)07340-2]

The magnetic moment of 11 Be (T 1͞2 13.8 s) was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a 11 Be 1 ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal, and observation of rf resonances in the asymmetric angular distribution of the b decay (b-NMR). The nuclear magnetic moment m͑ 11 Be͒ 21.6816͑8͒ m N provides a stringent test for theoretical models describing the structure of the 1͞2 1 neutron halo state.

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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.

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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).

We report the first application of an ultrasensitive detection scheme in on-line collinear-laser spectroscopy. It is based on radioactive detection of optical depopulation pumping, using state-selective charge exchange as an intermediate step. This extends the calcium isotope shift measurements beyond the fm shell closure. The extracted ^'Ca mean-square charge radius constitutes the first experimentally determined one of a short-lived neutron-rich isotope beyond the A^=28 shell closure. The steep increase in radius after the doubly magic "^^^Ca nucleus indicates a strong coupling between the pm neutrons and the core protons.PACS numbers: 21.10.Ft, 27.40.+Z, 32.80. Bx During the past decade, collinear-laser spectroscopy at on-line mass separators has provided a wealth of new information about nuclear spins, moments, and radii by the development and the application of techniques with increasing sensitivity. Recent methods exploit the strong optical depopulation pumping of the initial atomic (ionic) state to detect the optical resonances by state-selective charge-changing collisions and ion (atom) counting instead of the less efficient photon counting [1-5]. The sensitivity limit is in many cases determined by the presence of strong beams of stable or long-lived isobars, superimposed on the weak beams of short-lived isotopes. One type of solution to this background problem would be the development of element selective (laser) ion sources, or very-high-resolution mass separators. We used radioactive detection of the optically pumped ions after stateselective charge exchange (later referred to as ROC) to avoid the influence of stable isobaric contaminants. In this Letter, we report the first application of this method to extend the calcium isotope shift measurements beyond the N =2S shell closure, thereby also providing the first experimentally determined charge radius for a short-lived isotope in the 20:< Z < 28, A^ > 28 mass region.The charge distribution of the isotopes in the calcium chain has been investigated extensively (see Ref.[6] and references therein), so far covering all isotopes from "^^Ca to "^^Ca, both being doubly magic nuclei. All existing laser spectroscopy data were calibrated with muonic isotope shifts combined with electron scattering data in a comprehensive analysis [6], yielding a parabolic dependence of the mean-square charge radii as a function of neutron number, with a pronounced odd-even staggering. Several Hartree-Fock-based calculations have been performed by Caurier and Poves [7], Waroquier, Heyde, and Wenes [8], and Barranco and Broglia [9], finally resulting in a good agreement with experiment. Both the parabolic trend and the odd-even staggering were also reproduced by Talmi [10] using a shell-model-based theory. An extension of the isotope shift and nuclear moment data across the A^ =28 shell closure is of fundamental interest as it provides a crucial test for Hartree-Fock calculations and for shell model descriptions far from stability.Nuclear spectroscopy experiments show, as expec...