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The decay of the neutron-rich and was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number above the shell. The -delayed -ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three -decay branches of were established, two of which were observed for the first time. Population of neutron-unbound states decaying via rays was identified in the two daughter nuclei of and , at excitation energies exceeding the neutron separation energy by 1 MeV. The -delayed one- and two-neutron emission branching ratios of were determined and compared with theoretical calculations. The -delayed one-neutron decay was observed to be dominant -decay branch of even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of . Transitions following the decay of are reported for the first time, including rays tentatively attributed to . In total, six new levels were identified in on the basis of the coincidences observed in the and decays. A transition that might be a candidate for deexciting the missing neutron single-particle state in was observed in both decays and its assignment is discussed. Experimental level schemes of and are compared with shell-model predictions. Using the fast timing technique, half-lives of the , and levels in were determined. From the lifetime of the state measured for the first time, an unexpectedly large transition strength was deduced, which is not reproduced by the shell-model calculations.

The mean-square charge radii of $^{207,208}$Hg ($Z=80, N=127,128$) have been studied for the first time and those of $^{202,203,206}$Hg ($N=122,123,126$) remeasured by the application of in-source resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic \textit{kink} in the charge radii at the $N=126$ neutron shell closure has been revealed, providing the first information on its behavior below the $Z=82$ proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and non-relativistic Hartree-Fock-Bogoliubov approaches, considering both the new mercury results and existing lead data. Contrary to previous interpretations, it is demonstrated that both the kink at $N=126$ and the odd-even staggering (OES) in its vicinity can be described predominately at the mean-field level, and that pairing does not need to play a crucial role in their origin. A new OES mechanism is suggested, related to the staggering in the occupation of the different neutron orbitals in odd- and even-$A$ nuclei, facilitated by particle-vibration coupling for odd-$A$ nuclei., Comment: 7 pages, 5 figures, Physical Review C, in press

A study of the laser-ionized and mass-separated neutron-deficient isotopes $^{176,177,179}$Au was performed using the Resonance Ionization Laser Ion Source and the Windmill detection setup at ISOLDE, CERN. New and improved data on complex fine-structure α decays of the three isotopes were deduced, providing insight into the low-lying levels in the daughter nuclei $^{172,173,175}$Ir. New information on the properties of β-decay daughter products $^{177,179}$Pt was also obtained. From the first in-source laser spectroscopy measurements of the hyperfine structure in the atomic 267.6-nm transition of 176Au, the nuclear magnetic moments for both high- and low-spin α-decaying states were deduced. Together with the values determined from the additivity relations, they were used to propose the most probable spins and configurations for both states. The α-decay branching ratios were determined as $b_{\alpha}$ $\left (^{176}\textrm{Au}^{ls}\right)=58(5)$% and $b_{\alpha}$ $(^{176} \textrm{Au}^{hs})=29(5)$%.

International audience; $β$-delayed fission ($β$DF) decay of a low-spin (ls) and a high-spin (hs) isomer in $^{188}$Bi was studied at the ISOLDE facility at CERN. Isomer-selective laser ionization and time gating were employed to investigate each isomer separately and their $β$DF partial half-lives were determined: $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{ls}})=5.6(8)×10^3$ s and $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{hs}})=1.7(6)×10^3$ s. This work is the first βDF study of two states in one isotope and allows the spin dependence of low-energy fission to be explored. The fission fragment mass distribution of a daughter nuclide $^{188}$Pb, following the $β$ decay of the high-spin isomer, was deduced and indicates a mixture of symmetric and asymmetric fission modes. Experimental results were compared with self-consistent mean-field calculations based on the finite-range Gogny D1M interaction. To reproduce the measured $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{hs}})$, the calculated fission barrier of $^{188}$Pb had to be reduced by ≈30%. After this reduction, the measured $T_{1/2\mathrm{p},β\mathrm{DF}} (^{188}\mathrm{Bi^{ls}})$ was in agreement with calculations for a few possible configurations for $^{188}\mathrm{Bi^{ls}}$. Theoretical $β$DF probabilities for these configurations were found to be lower by a factor of 4–9 than the $β$DF probability of $^{188}\mathrm{Bi^{hs}}$. The fission fragment mass distribution of $^{188}$Pb was compared to the scission-point model SPY and the calculations based on the finite-range liquid-drop model. The first observation of $β$DF for $^{190}$Bi is also reported.

© 2019 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. Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in At217,218,219 have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope At218 has been found to be larger than the average of its even-N neighbors, At217,219. The discrepancy between the additivity-rule prediction and experimental data for the magnetic moment of At218 also supports the possible presence of octupole collectivity in the considered nuclei. ispartof: Physical Review C vol:99 issue:5 status: published

The neutron-rich isotopes ^{58-63}Cr were produced for the first time at the ISOLDE facility and their masses were measured with the ISOLTRAP spectrometer. The new values are up to 300 times more precise than those in the literature and indicate significantly different nuclear structure from the new mass-surface trend. A gradual onset of deformation is found in this proton and neutron midshell region, which is a gateway to the second island of inversion around N=40. In addition to comparisons with density-functional theory and large-scale shell-model calculations, we present predictions from the valence-space formulation of the ab initio in-medium similarity renormalization group, the first such results for open-shell chromium isotopes. ispartof: PHYSICAL REVIEW LETTERS vol:120 issue:23 ispartof: location:United States status: published

The neutron-rich isotopes $^{58-63}$Cr were produced for the first time at the ISOLDE facility and their masses were measured with the ISOLTRAP spectrometer. The new values are up to 300 times more precise than those in the literature and indicate significantly different nuclear structure from the new mass-surface trend. A gradual onset of deformation is found in this proton and neutron mid-shell region, which is a gateway to the second island of inversion around \emph{N}=40. In addition to comparisons with density-functional theory and large-scale shell-model calculations, we present predictions from the valence-space formulation of the \emph{ab initio} in-medium similarity renormalization group, the first such results for open-shell chromium isotopes., Comment: 6 pages, 3 figures, 1 table

Physical review letters 120(23), 232501 (2018). doi:10.1103/PhysRevLett.120.232501, Published by APS, College Park, Md.

Physical review / C 97(5), 054327 (2018). doi:10.1103/PhysRevC.97.054327, Published by Inst., Woodbury, NY

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron-deficient isotopes Tl179-184 using the 276.9-nm transition. The experiment has been performed at the CERN-Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in Tl179,181,183 have been determined as I=1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in Tl182,184 from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes Tl179-184 follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of Tl183,184 has been observed, suggesting a larger deformation for the intruder-based 9/2- and 10- states compared to the ground states. An unexpected growth of the isomer shift for Tl183 has been found.

Direct mass measurements of the low-spin 3/2− and high-spin 13/2+ states in the neutron-deficient isotopes Po195 and Po197 were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the νi13/2 orbital in Po195,197. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from α-decay chains. These excitation energies complete the knowledge of the energy systematics in the region and confirm that the 13/2+ states remain isomeric, independent of the number of valence neutrons. Direct mass measurements of the low-spin $3/2^{(-)}$ and high-spin $13/2^{(+)}$ states in the neutron-deficient isotopes $^{195}$Po, $^{197}$Po, and high-spin $13/2^{(+)}$ state in $^{199}$Po were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the $\nu$i$_{13/2}$ orbital in $^{195,197}$Po. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from $\alpha$-decay chains. The new excitation energies complete the knowledge of the energy systematics in the region and confirm for the first time that the $13/2^{(+)}$ states remain isomeric, independent of the number of valence neut

A detailed α-decay spectroscopy study of 180Tl has been performed at ISOLDE (CERN). Z-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of 180Tl. Fine-structure α decays to excited levels in the daughter 176Au were identified and an α-decay scheme of 180Tl was constructed based on an analysis of α−γ and α−γ−γ coincidences. Multipolarities of several γ-ray transitions deexciting levels in 176Au were determined. Based on the analysis of reduced α-decay widths, it was found that all α decays are hindered, which signifies a change of configuration between the parent and all daughter states. ispartof: Physical Review C vol:96 issue:5 status: published

A nuclear-decay spectroscopy study of the neutron-deficient isotope At196 is reported where an isotopically pure beam was produced using the selective Resonance Ionization Laser Ion Source and On-Line Isotope Mass Separator (CERN). The fine-structure α decay of At196 allowed the low-energy excited states in the daughter nucleus Bi192 to be investigated. A β-delayed fission study of At196 was also performed. A mixture of symmetric and asymmetric fission-fragment mass distributions of the daughter isotope Po196 (populated by β decay of At196) was deduced based on the measured fission-fragment energies. A βDF probability PβDF(At196)=9(1)×10-5 was determined.

The β decay of [superscript 192,190]Pb has been studied using the total absorption technique at the ISOLDE (CERN) facility. The β-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the [superscript 192,190]Pb isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects., Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FPA2008-06419-C02-01), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FPA2011-24553), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FPA2013-41267-P), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FPA2014-52823-C2-1-P), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FRPA2012-32443), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project FIS2011-23565), Spain. Ministerio de Ciencia e Innovacion y Ministerio de Economia y Competitividad (Project CSD-2007-00042), Seventh Framework Programme (European Commission) (ENSAR Contract 262010), Seventh Framework Programme (European Commission) (Contract PIOF-GA-2011-298364), Orszagos Tudomanyos Kutatasi Alapprogramok (OTKA) (Contract K100835), Orszagos Tudomanyos Kutatasi Alapprogramok (OTKA) (Contract K106035)

Hyperfine splitting parameters have been measured for the neutron-deficient odd-mass polonium isotopes and isomers Po-193-203(g,m), Po-209,Po-211. The measurement was performed at the ISOLDE (CERN) online mass separator using the in-source resonance ionization spectroscopy technique. The magnetic dipole moments mu and spectroscopic electric quadrupole moments Q(S) have been deduced. Their implication for the understanding of nuclear structure in the vicinity of the closed proton shell at Z = 82 and the neutron mid-shell at N = 104 is discussed. For the most neutron-deficient nuclei (A = 193,195,197), a deviation of mu and QS from the nearly constant values for heavier polonium nuclei was observed. Particle-plus-rotor calculations with static oblate deformation describe the electromagnetic moments for these nuclei well, provided a gradual increase of a mean deformation when going to lighter masses is assumed for the polonium nuclei with A < 198.

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope 178Tl has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of 178Tl to be produced. The first identification of the β-delayed fission of this isotope was made and its probability PβDF(178Tl)=0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope 178Hg (populated by the β decay of 178Tl) was deduced based on the measured fission fragment energies. The fine-structure α-decay pattern of 178Tl allowed the low-energy states in the daughter nucleus 174Au to be studied.

The detailed analysis of the beta-delayed fission data of Tl-180 is presented. The experiment was performed by producing a pure beam of Tl-180 by means of highly selective resonance laser ionization followed by mass separation with the ISOLDE (CERN, Geneva) isotope separator. A surprising asymmetric mass distribution of fission fragments from Hg-180, the daughter of Tl-180 beta decays, was observed. Here, the energy calibration of the silicon detectors, which is crucial for a proper determination of the fission fragments' energy and mass split, is presented and the total kinetic energy and its dependence on the mass split ratio is discussed. A more precise beta-delayed fission probability P-beta DF(Tl-180) = 3.2(2) x 10(-3)% was deduced.

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope 178Tl has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of 178Tl to be produced. The first identification of the β-delayed fission of this isotope was made and its probability PβDF(178Tl) = 0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope 178Hg (populated by the β decay of 178Tl) was deduced based on the measured fission fragment energies. The fine-structure α-decay pattern of 178Tl allowed the low-energy states in the daughter nucleus 174 Au to be studied. ispartof: Physical Review C, Nuclear Physics vol:88 issue:4 pages:1-10 status: published

On account of its high efficiency, speed and unmatched selectivity, the Resonance Ionization Laser Ion Source (RILIS) is the preferred method for ionizing the nuclear reaction products at the ISOLDE on-line isotope separator facility. [...]

A beta-decay study of Cu-77 has been performed at the ISOLDE mass separator with the aim to deduce its beta-decay properties and to obtain spectroscopic information on Zn-77. Neutron-rich copper isotopes were produced by means of proton- or neutron-induced fission reactions on U-238. After the production, Cu-77 was selectively laser ionized, mass separated and sent to different detection systems where beta-gamma and beta-n coincidence data were collected. We report on the deduced half-live, decay scheme, and possible spin assignment of 77Cu. A beta-decay study of Cu-77 has been performed at the ISOLDE mass separator with the aim to deduce its beta-decay properties and to obtain spectroscopic information on Zn-77. Neutron-rich copper isotopes were produced by means of proton- or neutron-induced fission reactions on U-238. After the production, Cu-77 was selectively laser ionized, mass separated and sent to different detection systems where beta-gamma and beta-n coincidence data were collected. We report on the deduced half-live, decay scheme, and possible spin assignment of 77Cu.

The $B(E2;0^+\to2^+)$ value in $^{68}$Ni has been measured using Coulomb excitation at safe energies. The $^{68}$Ni radioactive beam was post-accelerated at the ISOLDE facility (CERN) to 2.9 MeV/u. The emitted $\gamma$ rays were detected by the MINIBALL detector array. A kinematic particle reconstruction was performed in order to increase the measured c.m. angular range of the excitation cross section. The obtained value of 2.8$\pm$1.0 10$^2$ e$^2$fm$^4$ is in good agreement with the value measured at intermediate energy Coulomb excitation, confirming the low transition probability.

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.

A beta -decay study of the even mass /sup 74,76,78/Cu isotopes toward levels in /sup 74,76,78/Zn was performed at the ISOLDE mass separator. The copper isotopes were produced in proton- or neutron- induced fission reactions on /sup 238/U, laser ionized, mass separated, and sent to a beta - gamma detection system. Half-lives, decay schemes, and possible spin configurations were obtained for the copper isotopes. The results are compared with calculations using schematic forces as well as large-scale shell-model calculations with realistic forces.