R.P. de Groote

Use of a Continuous Wave Laser and Pockels Cell for Sensitive High-Resolution Collinear Resonance Ionization Spectroscopy.

New technical developments have led to a 2 orders of magnitude improvement of the resolution of the collinear resonance ionization spectroscopy (CRIS) experiment at ISOLDE, CERN, without sacrificing the high efficiency of the CRIS technique. Experimental linewidths of 20(1) MHz were obtained on radioactive beams of francium, allowing us for the first time to determine the electric quadrupole moment of the short lived [t_{1/2}=22.0(5) ms] ^{219}Fr Q_{s}=-1.21(2) eb, which would not have been possible without the advantages offered by the new method. This method relies on a continuous-wave laser and an external Pockels cell to produce narrow-band light pulses, required to reach the high resolution in two-step resonance ionization. Exotic nuclei produced at rates of a few hundred ions/s can now be studied with high resolution, allowing detailed studies of the anchor points for nuclear theories.

Towards high-resolution laser ionization spectroscopy of the heaviest elements in supersonic gas jet expansion

Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability. The technique is characterized in a measurement on actinium isotopes around the N=126 neutron shell closure. A significant improvement in the spectral resolution by more than one order of magnitude is achieved in these experiments without loss in efficiency.

Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich 218m,219,229,231Fr isotopes were measured with the newly installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at the On-Line Isotope Mass Separator (ISOLDE), CERN, probing the 7s2S1/2 to 8p2P3/2 atomic transition. The ??r2?A,221 values for 218m,219Fr and 229,231Fr follow the observed increasing slope of the charge radii beyond N = 126. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that 220Fr has a weakly inverted odd-even staggering while 228Fr has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The g(219Fr) = +0.69 (1) value supports a ?1h9/2 shell-model configuration for the ground state. The g(229,231Fr) valuessupportthetentativeI?(229,231Fr)=(1/2+) spin and point to a ?s?1 intruder ground-state configuration.

arXiv : Dipole and quadrupole moments of

Nuclear spins and precise values of the magnetic dipole and electric quadrupole moments of the ground-states of neutron-rich

^{73-78}

^{76-78}

Cu as a test of the robustness of the

Cu isotopes were measured using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, CERN. The nuclear moments of the less exotic

Z=28

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shell closure near

Cu isotopes were re-measured with similar precision, yielding values that are consistent with earlier measurements. The moments of the odd-odd isotopes, and

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^{78}_{29}

Ni

Cu (