638 research outputs found

    Test of a high power target design

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    Test of a high power tantalum target

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    Laser Spectroscopy of Niobium Fission Fragments: First Use of Optical Pumping in an Ion Beam Cooler Buncher

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    A new method of optical pumping in an ion beam cooler buncher has been developed to selectively enhance ionic metastable state populations. The technique permits the study of elements previously inaccessible to laser spectroscopy and has been applied here to the study of Nb. Model independent mean-square charge radii and nuclear moments have been studied for 90,90m,91,91m,92,93,99,101,103^{90,90 m,91,91 m,92,93,99,101,103}Nb to cover the region of the N=50 shell closure and N≈60 sudden onset of deformation. The increase in mean-square charge radius is observed to be less than that for Y, with a substantial degree of ÎČ softness observed before and after N=60

    Recent results in nuclear astrophysics at the n_TOF facility at CERN

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    The neutron time of flight (n_TOF) facility at CERN is a spallation source characterized by a white neutron spectrum. The innovative features of the facility, in the two experimental areas, (20 m and 185 m), allow for an accurate determination of the neutron cross section for radioactive samples or for isotopes with small neutron capture cross section, of interest for Nuclear Astrophysics. The recent results obtained at n_TOF facility are presented

    Quadrupole moments and mean-square charge radii in the bismuth isotope chain

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    Isotope shifts and hyperfine structures of the 205,206,208,210,210m,212,213^{205, 206, 208, 210, 210m, 212, 213}Bi isotopes have been studied on the 306.7nm line using gas cell laser spectroscopy. The neutron-rich isotopes are the first isotones of Pb to be measured immediately above the N=126 shell closure. The ground state quadrupole moments of the even--N isotopes increase as neutrons are added or removed from the N=126 shell, but no corresponding increase is observed in the charge radii

    Isomer shift and magnetic moment of the long-lived 1/2+^{+} isomer in 3079^{79}_{30}Zn49_{49}: signature of shape coexistence near 78^{78}Ni

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    Collinear laser spectroscopy has been performed on the 3079^{79}_{30}Zn49_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life was confirmed, and the nuclear spins and moments of the ground and isomeric states in 79^{79}Zn as well as the isomer shift were measured. From the observed hyperfine structures, spins I=9/2I = 9/2 and I=1/2I = 1/2 are firmly assigned to the ground and isomeric states. The magnetic moment ÎŒ\mu (79^{79}Zn) = −-1.1866(10) ÎŒN\mu_{\rm{N}}, confirms the spin-parity 9/2+9/2^{+} with a Îœg9/2−1\nu g_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment ÎŒ\mu (79m^{79m}Zn) = −-1.0180(12) ÎŒN\mu_{\rm{N}} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50N = 50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state: ή⟹rc2⟩79,79m\delta \langle r^{2}_{c}\rangle^{79,79m} = +0.204(6) fm2^{2}, providing first evidence of shape coexistence.Comment: 5 pages, 4 figures, 1 table, Accepeted by Phys. Rev. Lett. (2016

    Decay-assisted collinear resonance ionization spectroscopy: Application to neutron-deficient francium

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    This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes 202−206^{202-206}Fr performed with the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the ISOLDE facility, CERN. The high resolution innate to collinear laser spectroscopy is combined with the high efficiency of ion detection to provide a highly-sensitive technique to probe the hyperfine structure of exotic isotopes. The technique of decay-assisted laser spectroscopy is presented, whereby the isomeric ion beam is deflected to a decay spectroscopy station for alpha-decay tagging of the hyperfine components. Here, we present the first hyperfine-structure measurements of the neutron-deficient francium isotopes 202−206^{202-206}Fr, in addition to the identification of the low-lying states of 202,204^{202,204}Fr performed at the CRIS experiment.Comment: Accepted for publication with Physical Review

    Nuclear spins, magnetic moments and quadrupole moments of Cu isotopes from N = 28 to N = 46: probes for core polarization effects

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    Measurements of the ground-state nuclear spins, magnetic and quadrupole moments of the copper isotopes from 61Cu up to 75Cu are reported. The experiments were performed at the ISOLDE facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the N=28 and N=50 shell closures is reasonably reproduced by large-scale shell-model calculations starting from a 56Ni core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is however strongly reduced at N=40 due to the parity change between the pfpf and gg orbits. No enhanced core polarization is seen beyond N=40. Deviations between measured and calculated moments are attributed to the softness of the 56Ni core and weakening of the Z=28 and N=28 shell gaps.Comment: 13 pagers, 19 figures, accepted by Physical Review
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