Search

The hyperfine spectra of Mn-51,Mn-53-64 were measured in two experimental runs using collinear laser spectroscopy at ISOLDE, CERN. Laser spectroscopy was performed on the atomic 3d(5) 4s(2) S-6(5/2) -> 3d(5) 4s4p P-6(3/2) and ionic 3d(5) 4s S-5(2) -> 3d(5) 4p P-5(3) transitions, yielding two sets of isotope shifts. The mass and field shift factors for both transitions have been calculated in the multiconfiguration Dirac-Fock framework and were combined with a King plot analysis in order to obtain a consistent set of mean-square charge radii which, together with earlier work on neutron-deficient Mn, allow the study of nuclear structure changes from N = 25 across N = 28 up to N = 39. A clear development of deformation is observed towards N = 40, confirming the conclusions of the nuclear moments studies. From a Monte Carlo shell-model study of the shape in the Mn isotopic chain, it is suggested that the observed development of deformation is not only due to an increase in static prolate deformation but also due to shape fluctuations and triaxiality. The changes in mean-square charge radii are well reproduced using the Duflo-Zuker formula except in the case of large deformation.

© 2018 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. The neutron-deficient cadmium isotopes have been measured by high-resolution laser spectroscopy at CERN-ISOLDE. The electromagnetic moments of Cd101 have been determined for the first time and the quadrupole-moment precision of Cd103 has been vastly improved. The results on the sequence of 5/2+ ground states in Cd101-109 are tentatively discussed in the context of simple structure in complex nuclei as similarities are found with the 11/2- states in the neutron-rich cases. Comparison with shell-model calculations reveals a prominent role of the two holes in the Z=50 core. ispartof: Physical Review C vol:98 issue:1 status: published

The neutron-deficient cadmium isotopes have been measured by high-resolution laser spectroscopy at CERN-ISOLDE. The electromagnetic moments of 101Cd have been determined for the first time and the quadrupole-moment precision of 103Cd has been vastly improved. The results on the sequence of 5/2+ ground states in 101–109Cd are tentatively discussed in the context of simple structure in complex nuclei as similarities are found with the 11/2− states in the neutron-rich cases. Comparison with shell-model calculations reveals a prominent role of the two holes in the Z=50 core.

Nuclear ground-state properties, such as spin, charge radius, and magnetic dipole and electric quadrupole moments are important quantities to describe the nucleus. The comparison of experimental data to shell-model calculations gives insight in the underlying nuclear structure and composition of ground-state wave functions. Spins and charge radii can also be used to test the predictions of state-of-the-art microscopic models. This work contributes to these studies providing new measurements in the region of the nuclear chart around the magic proton number Z = 20. The data have been obtained at the collinear laser spectroscopy setup COLLAPS located at the radioactive-ion-beam facility ISOLDE at CERN. Using bunched-beam laser spectroscopy hyperfine structure spectra of the potassium isotopes with mass number A = 48 - 51 could be recorded for the first time. Ground-state spins and isotope shifts could be deduced for 48-51K contributing to the evolution of the πd3=2 orbital beyond the shell closure at the magic neutron number N = 28. Charge radii deduced from isotope shifts provide information towards the systematics of the charge radii in the calcium region beyond the N = 28 shell closure. While theoretical calculations predict the correct spins, the charge radii still provide a challenge even to the newest relativistic mean-field and coupled cluster models.

Isomer shifts have been determined in 111–129Cd by high-resolution laser spectroscopy at CERN ISOLDE. The corresponding mean square charge-radii changes, from the 1/2+ and the 3/2+ ground states to the 11/2− isomers, have been found to follow a distinct parabolic dependence as a function of the atomic mass number. Since the isomers have been previously associated with simplicity due to the linear mass dependence of their quadrupole moments, the regularity of the isomer shifts suggests a higher order of symmetry affecting the ground states in addition. A comprehensive description assuming nuclear deformation is found to accurately reproduce the radii differences in conjunction with the known quadrupole moments. This intuitive interpretation is supported by covariant density functional theory. ispartof: Physical Review Letters vol:116 issue:3 pages:1-5 ispartof: location:United States status: published

A marked difference in the nuclear charge radius was observed between the Iπ=3+ ground state and the Iπ=0+ isomer of K38 and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of ⟨r2c⟩(⟨r2c⟩(38Km)− ⟨r2c⟩( (38Kg)=0.100(6) fm2 was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in K38 have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N,Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of Ca40.

International audience

Physics letters / B 731, 97 - 102 (2014). doi:10.1016/j.physletb.2014.02.012, Published by North-Holland Publ., Amsterdam

A marked difference in the nuclear charge radius was observed between the I/pi = 3+ ground state and the I/pi = 0+ isomer of 38K and is qualitatively explained using an intuitive picture of proton-neutron pairing. In a high-precision measurement of the isomer shift using bunched-beam collinear laser spectroscopy at CERN-ISOLDE, a change in the mean-square charge radius of (r_c^2)(38Km)-(r_c^2)(38Kg)=0.100(6)fm^2 was obtained. This is an order of magnitude more accurate than the result of a previous indirect measurement from which it was concluded that both long-lived states in 38K have similar charge radii. Our observation leads to a substantially different understanding since the difference in charge radius is, moreover, opposite in sign to previously reported theoretical predictions. It is demonstrated that the observed isomer shift can be reproduced by large-scale shell-model calculations including proton and neutron excitations across the N, Z=20 shell gaps, confirming the significance of cross-shell correlations in the region of 40Ca. ispartof: PHYSICAL REVIEW LETTERS vol:113 issue:5 pages:052502-5 ispartof: location:United States status: published

The neutron-rich isotopes of cadmium up to the N=82 shell closure have been investigated by high-resolution laser spectroscopy. Deep-uv excitation at 214.5 nm and radioactive-beam bunching provided the required experimental sensitivity. Long-lived isomers are observed in Cd127 and Cd129 for the first time. One essential feature of the spherical shell model is unambiguously confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably, this mechanism is found to act well beyond the h11/2 shell.

Collinear laser spectroscopy was performed on the 63,64,66,68−82Ga isotopes with neutron numbers from N=32 to N=51. These measurements were carried out at the ISOLDE radioactive ion beam facility at CERN. Here we present the nuclear mean-square charge radii extracted from the isotope shifts and, for the lighter isotopes, new spin and moment values. New ground-state nuclear spin and moments were extracted from the hyperfine spectra of 63,70Ga, measured on an atomic transition in the neutral atom. The ground-state spin of 63Ga is determined to be I=3/2. Analysis of the trend in the change in mean-square charge radii of the gallium isotopes demonstrates that there is no evidence of anomalous charge radii behavior in gallium in the region of N=32.

The nuclear charge radius of $^{12}$Be was precisely determined using the technique of collinear laser spectroscopy on the $2s_{1/2}\rightarrow 2p_{1/2, 3/2}$ transition in the Be$^{+}$ ion. The mean square charge radius increases from $^{10}$Be to $^{12}$Be by $\delta ^{10,12} = 0.69(5) \fm^{2}$ compared to $\delta ^{10,11} = 0.49(5) \fm^{2}$ for the one-neutron halo isotope $^{11}$Be. Calculations in the fermionic molecular dynamics approach show a strong sensitivity of the charge radius to the structure of $^{12}$Be. The experimental charge radius is consistent with a breakdown of the N=8 shell closure., Comment: 5 pages, 3 figures

Charge radii of all magnesium isotopes in the sd shell have been measured, revealing evolution of the nuclear shape throughout two prominent regions of assumed deformation centered on 24Mg and 32Mg. A striking correspondence is found between the nuclear charge radius and the neutron shell structure. The importance of cluster configurations towards N=8 and collectivity near N=20 is discussed in the framework of the fermionic molecular dynamics model. These essential results have been made possible by the first application of laser-induced nuclear orientation for isotope shift measurements.

Collinear laser spectroscopy was performed on the 63,64,66,68−82Ga isotopes with neutron numbers from N = 32 to N = 51. These measurements were carried out at the ISOLDE radioactive ion beam facility at CERN. Here we present the nuclear mean-square charge radii extracted from the isotope shifts and, for the lighter isotopes, new spin and moment values. New ground-state nuclear spin and moments were extracted from the hyperfine spectra of 63,70Ga, measured on an atomic transition in the neutral atom. The ground-state spin of 63Ga is determined to be I = 3/2. Analysis of the trend in the change in mean-square charge radii of the gallium isotopes demonstrates that there is no evidence of anomalous charge radii behavior in gallium in the region of N = 32. ispartof: Physical Review C, Nuclear Physics vol:86 issue:3 status: published

Collinear laser spectroscopy was performed on the 63,64,66,68−82Ga isotopes with neutron numbers from N = 32 to N = 51. These measurements were carried out at the ISOLDE radioactive ion beam facility at CERN. Here we present the nuclear mean-square charge radii extracted from the isotope shifts and, for the lighter isotopes, new spin and moment values. New ground-state nuclear spin and moments were extracted from the hyperfine spectra of 63,70Ga, measured on an atomic transition in the neutral atom. The ground-state spin of 63Ga is determined to be I = 3/2. Analysis of the trend in the change in mean-square charge radii of the gallium isotopes demonstrates that there is no evidence of anomalous charge radii behavior in gallium in the region of N = 32. peerReviewed