Search

A new β-decaying state in 214Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred Iπ = (8−) assignment was suggested for this state based on the β-decay feeding pattern to levels in 214Po and shell-model calculations. The half-life of the Iπ = (8−) state was deduced to be T1/2 = 9.39(10) min. The deexcitation of the levels populated in 214Po by the β decay of this state was investigated via γ -γ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in 214Bi and 214Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new β-decaying state as an Iπ = 8− isomer and allow for tentative assignment of shell-model states to several high-spin states in 214Po. peerReviewed

International audience; A new $\beta$-decaying state in $^{214}$Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred $I^{\pi} = (8^-)$ assignment was suggested for this state based on the β-decay feeding pattern to levels in $^{214}$Po and shell-model calculations. The half-life of the $I^{\pi} = (8^-)$ state was deduced to be $T_{1/2} = 9.39(10)$ min. The deexcitation of the levels populated in $^{214}$Po by the $\beta$ decay of this state was investigated via $\gamma - \gamma$ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in $^{214}$Bi and $^{214}$Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both calculations agree on the interpretation of the new β-decaying state as an $I^{\pi} = 8^-$ isomer and allow for tentative assignment of shell-model states to several high-spin states in $^{214}$Po.

We demonstrate a continuously tunable, multi-Stokes Raman laser operating in the visible range (420 - 600 nm). Full spectral coverage was achieved by efficiently cascading the Raman shifted output of a tunable, frequency-doubled Ti:Sapphire laser. Using an optimized hemi-spherical external Raman cavity composed only of a diamond crystal and a single reflecting mirror, producing high power output at high conversion efficiency (>60 % from pump to Stokes) for a broad range of wavelengths across the visible. Enhancement of the cascading was achieved by controlling the polarization state of the pump and Stokes orders. The Stokes outputs exhibited a linewidth of 11 ± 1 GHz for each order, resembling the pump laser linewidth, enabling its use for the intended spectroscopic applications. Furthermore, the Raman laser performance was demonstrated by applying it for the resonance excitation of atomic transitions in calcium.

International audience; A comprehensive study of the isotope $^{178}$Auhas been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in$^{178}$Auwere identified—a low-spin ground state and a high-spin isomer—each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in$^{178}$Auwas determined to be$E$$^{*}$=189(14)keV. Theα-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus$^{174}$Ir. Nuclear spin assignments of$I$($^{178}$Au$^{g}$)=(2,3)and$I$($^{178}$Aum)=(7,8)are made based on the observed$\beta$-decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for$^{178}$Au$^{g,m}$.

© 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. The structure of low-spin states originating from shape-coexisting configurations in Ni284068 was directly probed via the two-neutron transfer reaction Ni66(t,p)Ni68 in inverse kinematics using a radioactive ion beam on a radioactive target. The direct feeding to the first excited 0+ state was measured for center-of-mass angles 4-16 and amounts to an integral of 4.2(16)% relative to the ground state. The observed difference in feeding of the 0+ states is explained by the transfer of neutrons, mainly in the pf shell below N=40 for the ground state, and across N=40 in the g9/2 orbital for the 02+, based on second-order distorted-wave Born approximation calculations combined with state-of-the-art shell-model two-nucleon amplitudes. However, the direct feeding to the 21+ state [29(3)%] is incompatible with these calculations. ispartof: Physical Review C vol:99 issue:5 pages:054332-054332 status: published

International audience; An α-decay study of At218 was performed at the CERN-ISOLDE facility. Laser-ionized beams of At218 were mass separated and implanted into an α-γ detection setup. Coincidence α-γ data were collected for the first time and a more precise half-life value of T1/2=1.27(6) s was measured. A new α-decay scheme was deduced based on the extracted reduced α-decay widths for fine-structure decays. The results from this work lead to a preferred spin and parity assignment of Jπ=(3−); however, Jπ=(2)− cannot be fully excluded.

International audience; Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in $^{217,218,219}$At 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 $^{218}$At has been found to be larger than the average of its even-$N$ neighbors, $^{217,219}$At. The discrepancy between the additivity-rule prediction and experimental data for the magnetic moment of $^{218}$At also supports the possible presence of octupole collectivity in the considered nuclei.

The first accurate measurements of the α-decay branching ratio and half-life of the Iπ=1/2+ ground state in $^{181}$Tl have been made, along with the first determination of the magnetic moments and I=1/2 spin assignments of the ground states in $^{177,179}$Au. The results are discussed within the complementary systematics of the reduced α-decay widths and nuclear g factors of low-lying, Iπ=1/2+ states in the neutron-deficient lead region. The findings shed light on the unexpected hindrance of the 1/2+→1/2+, $^{181}$Tl→g177Au$^{g}$ α decay, which is explained by a mixing of π3s1/2 and π2d3/2 configurations in $^{177}$Au$^{g}$, whilst $^{181}$Tl$^{g}$ remains a near-pure π3s1/2. This conclusion is inferred from the g factor of $^{177}$Au$^{g}$ which has an intermediate value between those of π3s1/2 and π2d3/2 states. A similar mixed configuration is proposed for the Iπ=1/2+ ground state of $^{179}$Au. This mixing may provide evidence for triaxial shapes in the ground states in these nuclei.

Background: Shell evolution can impact the structure of the nuclei and lead to effects such as shape coexistence. The nuclei around Ni68 represent an excellent study case, however, spectroscopic information of the neutron-rich, Z

International audience; 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.

No Abstract.

No Abstract.

International audience; A detailed $\alpha$-decay spectroscopy study of $^{180}\mathrm{Tl}$ 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 $^{180}\mathrm{Tl}$. Fine-structure $\alpha$ decays to excited levels in the daughter $^{176}\mathrm{Au}$ were identified and an $\alpha$-decay scheme of $^{180}\mathrm{Tl}$ was constructed based on an analysis of $\alpha$-$\gamma$ and $\alpha$-$\gamma$-$\gamma$ coincidences. Multipolarities of several $\gamma$-ray transitions deexciting levels in $^{176}\mathrm{Au}$ were determined. Based on the analysis of reduced $\alpha$-decay widths, it was found that all $\alpha$ decays are hindered, which signifies a change of configuration between the parent and all daughter states.

Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron-deficient isotopes 179–184Tl 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 179,181,183Tl 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 182,184Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes 179–184Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of 183,184Tl 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 183Tl has been found. ispartof: Physical Review C vol:95 issue:1 pages:1-12 status: published

Background: Shell evolution can impact the structure of the nuclei and lead to effects such as shape coexistence. The nuclei around 68Ni represent an excellent study case, however, spectroscopic information of the neutron-rich, Z

The beta decay of $^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the $^{192,190}$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. The β decay of Pb192,190 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 Pb192,190 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. The beta decay of $^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the $^{192,190}$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.

International audience

International audience

The ν g 9 / 2 , d 5 / 2 , s 1 / 2 orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below 68Ni. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby 67Ni nucleus, by performing a ( d , p ) -experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball γ-detection array and a newly-developed delayed-correlation technique as to investigate μs-isomers. Angular distributions of the ground state and multiple excited states in 67Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial ν g 9 / 2 (1007 keV) and ν d 5 / 2 (2207 keV and 3277 keV) single-particle strengths up to an excitation energy of 5.8 MeV. 50% of the ν d 5 / 2 single-particle strength relative to the ν g 9 / 2 -orbital is concentrated in and shared between the first two observed 5 / 2 + levels. A comparison with extended Shell Model calculations and equivalent (3He, d) studies in the region around 9040Zr50 highlights similarities for the strength of the negative-parity pf and positive-parity g 9 / 2 state, but differences are observed for the d 5 / 2 single-particle strength.

The νg9/2,d5/2,s1/2 orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below 68 Ni. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby 67 Ni nucleus, by performing a (d,p) -experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball γ -detection array and a newly-developed delayed-correlation technique as to investigate μs-isomers. Angular distributions of the ground state and multiple excited states in 67 Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial νg9/2 (1007 keV) and νd5/2 (2207 keV and 3277 keV) single-particle strengths up to an excitation energy of 5.8 MeV. 50% of the νd5/2 single-particle strength relative to the νg9/2 -orbital is concentrated in and shared between the first two observed 5/2+ levels. A comparison with extended Shell Model calculations and equivalent ( 3 He, d ) studies in the region around 90 40 Zr 50 highlights similarities for the strength of the negative-parity pf and positive-parity g9/2 state, but differences are observed for the d5/2 single-particle strength.

This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation, we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyze whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine-structure constant a was smaller at early epoch. We test the isotope-shift method by comparing the calculated and experimental isotope shift for the alkali-metal and alkali-metal-like atoms Na, Mg II, K, Ca II and Ba II. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in Si II and Si IV, Mg II, Zn II, and Ge II. ispartof: Physical Review C, Nuclear Physics vol:68 issue:3 pages:1-6 status: published

The $νg_{9/2} , d_{5/2}, s_{1/2}$ orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below $^{68}$Ni. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby $^{67}$Ni nucleus, by performing a ($d, p$)-experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV / u using a combination of the T-REX particle detectors, the Miniball $\gamma$-detection array and a newly-developed delayed-correlation technique as to investigate $\mu$s-isomers. Angular distributions of the ground state and multiple excited states in $^{67}$Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial $νg_{9/2}$ (1007 keV) and $νd_{5/2}$ (2207 keV and 3277 keV) single- particle strengths up to an excitation energy of 5.8 MeV. 50% of the $νd_{5/2}$ single-particle strength relative to the $νg_{9/2}$-orbital is concentrated in and shared between the first two observed 5/2$^{+}$ levels. A comparison with extended Shell Model calculations and equivalent ($^{3}$He, $d$) studies in the region around $^{90}_{40}$Zr$_{50}$ highlights similarities for the strength of the negative-parity pf and positive-parity $g_{9/2}$ state, but differences are observed for the $d_{5/2}$ single-particle strength.

Decay spectroscopy of Tl 184 has been performed at the CERN Isotope Separator On-Line (ISOLDE) facility. An excitation energy of 506.1(1) keV and a half-life of 47.1(7) ms of the intruder based (10 − ) state have been extracted. The internal decay characteristics of this state are determined and discussed, extending the systematics of such states in the even-mass thallium nuclei below neutron midshell at N=104 . The retardation factors of the isomeric M2 and E3 transitions are deduced and compared with retardation factors in neighboring odd-mass and even-mass thallium isotopes. The new information is combined with a review of hindered and unhindered α -decay data of Bi 187–192 populating levels in daughter nuclei Tl 183–188 and supports the interpretation of the intruder character of the (10 − ) state in Tl 184 .