Search results for "polonium"
showing 10 items of 16 documents
Preparation of negative ion beams for the determination of the electron affinity of polonium by laser photodetachment
2021
A letter of intent submitted to the ISOLDE and Neutron-Time-of-flight Committee (INTC) at CERN to prepare the negative ion beam as a step towards measuring the electron affinity of polonium at CRIS (ISOLDE).
Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes
2015
Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po196,198,200,202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po200,202, the transitional and diagonal matrix elements of the 2+1 state are determined. In Po196,198 multistep Coulomb excitation is observed, populating the 4+1,0+2, and 2+2 states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from Po196 onwards. Three model descriptions are used to compare to the data. Calculati…
Shape coexistence in neutron-deficient Hg188 investigated via lifetime measurements
2020
Background: Shape coexistence in the Z≈82 region has been established in mercury, lead, and polonium isotopes. For even-even mercury isotopes with 100≤N≤106 multiple fingerprints of this phenomenon are observed, which seems to be no longer present for N≥110. According to a number of theoretical calculations, shape coexistence is predicted in the Hg188 isotope. Purpose: The aim of this work was to measure lifetimes of excited states in Hg188 to infer their collective properties, such as the deformation. Extending the investigation to higher-spin states, which are expected to be less affected by band-mixing effects, can provide additional information on the coexisting structures. Methods: The…
Evolution of collective motion in light polonium nuclei
1998
The {gamma}-ray spectroscopy of even- and odd-mass isotopes of polonium have been studied using arrays of Ge detectors coupled to recoil-mass analyzers, including recoil-decay tagging techniques. The level energies and B(E2) branching ratios can be reproduced by theoretical frameworks which do not explicitly include proton particle-hole excitations across the Z = 82 shell, conclusions in contrast to those deduced from alpha-decay measurements.
Early onset of deformation in the neutron-deficient polonium isotopes
2012
In-source laser spectroscopy has been performed at CERN-ISOLDE with the RILIS laser ion source on Po-191-204,Po-206,Po-208-211,Po-216,Po-218. New information on the beta decay of Po-199 were extracted in the process, challenging previous results. Large-scale atomic calculations were performed to extract the changes in the mean-square charge radius delta from the isotope shifts. The delta for the even-A isotopes reveal a large deviation from the spherical droplet model for N < 116.
Collective 2$^{+1}$ excitations in$^{206}$Po and$^{208,210}$Rn
2016
In the present study, $B(E2; 2^{+}_{1}\rightarrow 0^{+}_{1})$ values have been measured in the 208,210Rn and 206Po nuclei through Coulomb excitation of re-accelerated radioactive beams in inverse kinematics at CERN-ISOLDE. These nuclei have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist. However, contributions from collective excitations are likely to be present when moving away from the N=126 closed shell. Such an effect is confirmed by the observed increased collectivity of the $2^{+}_{1}\rightarrow 0^{+}_{1}$ transitions. Experimental results have been interpreted with the aid of theoretical studies carried out within the BCS-based QRP…
Alpha decay of the new isotopes 188,189Po
1999
New neutron-deficient isotopes 188,189Po have been produced in the complete fusion reaction of 52Cr ions with a 142Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of α-γ and α-conversion electron coincidence measurements and of α-α position and time correlations. In 189Po a ground state to ground state α decay with Eα1= 7540(20) keV, T1/2= 5(1) ms and two fine structure α-decays at Eα2= 7264(15) keV and Eα3= 7316(15) keV have been observed. In 188Po (T1/2= 400+200 −150μs) a ground state to ground state α decay at Eα= 7915(25) keV and a fine structure α decay at Eα= 7350(40) keV have been found. Improved data o…
Resonant laser ionization of polonium at rilis-isolde for the study of ground- and isomer-state properties
2008
Three new ionization schemes for polonium have been tested with the resonant ionization laser ion source (RILIS) during the on-line production of 196Po in a UCx target at ISOLDE. The saturation of the atomic transitions has been observed and the yields of the isotope chain 193–198,200,202,204Po have been measured. This development provides the necessary groundwork for performing in-source resonant ionization spectroscopy on the neutron-deficient polonium isotopes (Z = 84). ispartof: Nuclear Instruments & Methods in Physics Research B vol:266 issue:19 pages:4403-4406 ispartof: location:FRANCE, Deauville status: published
Lifetimes of intruder states in [sup 186, 188]Pb and [sup 194]Po
2006
Low-lying structure of light radon isotopes
2002
The excited states in the neutron-deficient isotopes Rn have been populated using the Er(Ar,4n), Er(Ar,4n), and Er(Ar,4n) reactions at beam energies of 175, 182, and 177 MeV, respectively. Evaporation residues were selected using an in-flight gas-filled separator and implanted at the focal plane into a 16-element position-sensitive, passivated ion-implanted planar silicon detector. Prompt γ rays were observed at the target position using an array of Compton-suppressed germanium detectors. Correlation with the subsequent radioactive decay of associated recoiling ions in the silicon detector, recoil-γ and recoil-γ-γ coincidences were used to construct decay schemes of light radon isotopes. Me…