Ground-State Electromagnetic Moments of Calcium Isotopes

High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the $^{43-51}$Ca isotopes. The ground state magnetic moments of $^{49,51}$Ca and quadrupole moments of $^{47,49,51}$Ca were measured for the first time, and the $^{51}$Ca ground state spin $I=3/2$ was determined in a model-independent way. Our results provide a critical test of modern nuclear theories based on shell-model calculations using phenomenological as well as microscopic interactions. The results for the neutron-rich isotopes are in excellent agreement with predictions using interactions derived from chiral effective field theory including three-nucleon forces, while lighter isotopes illustrate the presence of particle-hole excitations of the $^{40}$Ca core in their ground state.Comment: Accepted as a Rapid Communication in Physical Review

Magnetic moments of 33^{33}Mg in time-odd relativistic mean field approach

The configuration-fixed deformation constrained relativistic mean field approach with time-odd component has been applied to investigate the ground-state properties of $^{33}$Mg with effective interaction PK1. The ground state of $^{33}$Mg has been found to be prolate deformed, $\beta_2=0.23$, with the odd neutron in $1/2[330]$ orbital and the energy -251.85 MeV which is close to the data -252.06 MeV. The magnetic moment $- 0.9134 \mu_\mathrm{N}$ is obtained with the effective electromagnetic current which well reproduces the data $- 0.7456 \mu_\mathrm{N}$ self-consistently without introducing any parameter. The energy splittings of time reversal conjugate states, the neutron current, the energy contribution from the nuclear magnetic potential, and the effect of core polarization are discussed in detail.Comment: 13 pages, 4 figure

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

Collinear laser spectroscopy has been performed on the $^{79}_{30}$Zn$_{49}$ 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 $^{79}$Zn as well as the isomer shift were measured. From the observed hyperfine structures, spins $I = 9/2$ and $I = 1/2$ are firmly assigned to the ground and isomeric states. The magnetic moment $\mu$ ($^{79}$Zn) = $-$1.1866(10) $\mu_{\rm{N}}$, confirms the spin-parity $9/2^{+}$ with a $\nu g_{9/2}^{-1}$ shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment $\mu$ ($^{79m}$Zn) = $-$1.0180(12) $\mu_{\rm{N}}$ supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the $N = 50$ 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: $\delta \langle r^{2}_{c}\rangle^{79,79m}$ = +0.204(6) fm$^{2}$, providing first evidence of shape coexistence.Comment: 5 pages, 4 figures, 1 table, Accepeted by Phys. Rev. Lett. (2016

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

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 $pf$ and $g$ 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

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

This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes $^{202-206}$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 $^{202-206}$Fr, in addition to the identification of the low-lying states of $^{202,204}$Fr performed at the CRIS experiment.Comment: Accepted for publication with Physical Review

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 $^{218m,219,229,231}\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\delta\langle r^{2}\rangle^{A,221}$ values for $^{218m,219}\text{Fr}$ and $^{229,231}\text{Fr}$ 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 $^{220}\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\text{Fr}$ 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 $g(^{219}\text{Fr}) = +0.69(1)$ value supports a $\pi 1h_{9/2}$ shell model configuration for the ground state. The $g(^{229,231}\text{Fr})$ values support the tentative $I^{\pi}(^{229,231}\text{Fr}) = (1/2^{+})$ spin, and point to a $\pi s_{1/2}^{-1}$ intruder ground state configuration.Comment: Accepted for publication with Physical Review

High-precision quadrupole moment reveals significant intruder component in 13 33Al20 ground state

The electric quadrupole moment of the Al201333 ground state, located at the border of the island of inversion, was obtained using continuous-beam β-detected nuclear quadrupole resonance (β-NQR). From the measured quadrupole coupling constant νQ=2.31(4) MHz in an α-Al2O3 crystal, a precise value for the electric quadrupole moment is extracted: |Qs(Al33)|=141(3) mb. A comparison with large-scale shell model calculations shows that Al33 has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the N=20 shell gap. Al33 therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal Z≥14 isotopesThis work was partly supported by the European Community FP6—Structuring the ERA—Integrated Infrastructure Initiative Contract EURONS No. RII3-CT-2004-506065, by the FWO-Vlaanderen, by the IAP programme of the Belgium Science Policy under Grants No. P6/23 and No. P7/12, by a grant of the MICINN (Spain) (FPA2011-29854), by the Nupnet network SARFEN (PRI-PIMMNUP-2011-1361), by MINECO (Spain) Centro de Excelencia Severo Ochoa Programme under Grant No. SEV-2012-0249, and by JSPS KAKENHI (Japan) Grants No. 21740204 and No. 15K05094. The experiment was carried out under Experimental Program E437

Magnetic moments of 68^{68}Cug,m^{g,m} and 70^{70}Cug,m1,m2^{g,m_{1},m_{2}} nuclei measured by in-source laser spectroscopy

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 deduced magnetic moments are $\mu( ^{68}$Cu$^{g}$, I$^{\pi}$ = 1$^+$) = +2.48(2)(7)$\mu_{N}$ ; $\mu(^{68}$Cu$^{m}$, I$^{\pi}$=6$^{-}$) = +1.24(4)(6)$\mu_{N}$ and $\mu(^{70}$Cu$^{m_{2}}$, I$^{\pi}$=1$^{+}$) = +1.86(4)(6)$\mu_{N}$ ; $\mu(^{70}$Cu$^{g}$, I$^{\pi}$=6$^{-}$) = +1.50(7)(8)$\mu_{N}$. The results of the scans analysis point out on existence of a new isomer in $^{70}$Cu$^{m_{1}}$. It's deduced magnetic moment is (-)3.50(7)(11)$\mu_{N}$ that is in a good agreement with I$^{\pi}$=3$^{-}$ assignment. 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