53 research outputs found

    Early onset of ground-state deformation in the neutron-deficient polonium isotopes

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    In-source resonant ionization laser spectroscopy of the even-AA polonium isotopes 192210,216,218^{192-210,216,218}Po has been performed using the 6p37s6p^37s 5S2^5S_2 to 6p37p6p^37p 5P2^5P_2 (λ=843.38\lambda=843.38 nm) transition in the polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in 200210^{200-210}Po with a previous data set allows to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by Beyond Mean Field calculations.Comment: As submitted to PR

    Detailed α-decay study of 180Tl

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    International audienceA detailed α\alpha-decay spectroscopy study of 180Tl^{180}\mathrm{Tl} has been performed at ISOLDE (CERN). ZZ-selective ionization by the Resonance Ionization Laser Ion Source (RILIS) coupled to mass separation provided a high-purity beam of 180Tl^{180}\mathrm{Tl}. Fine-structure α\alpha decays to excited levels in the daughter 176Au^{176}\mathrm{Au} were identified and an α\alpha-decay scheme of 180Tl^{180}\mathrm{Tl} was constructed based on an analysis of α\alpha-γ\gamma and α\alpha-γ\gamma-γ\gamma coincidences. Multipolarities of several γ\gamma-ray transitions deexciting levels in 176Au^{176}\mathrm{Au} were determined. Based on the analysis of reduced α\alpha-decay widths, it was found that all α\alpha decays are hindered, which signifies a change of configuration between the parent and all daughter states

    First beta-decay spectroscopy of In-135 and new beta-decay branches of In-134

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    The beta decay of the neutron-rich In-134 and In-135 was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number Z = 50 above the N = 82 shell. The beta-delayed gamma-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three beta-decay branches of In-134 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 In-134, Sn-134 and Sn-133, at excitation energies exceeding the neutron separation energy by 1 MeV. The beta-delayed one- and two-neutron emission branching ratios of In-134 were determined and compared with theoretical calculations. The beta-delayed one-neutron decay was observed to be dominant beta-decay branch of In-134 even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of Sn-134. Transitions following the beta decay of In-135 are reported for the first time, including. rays tentatively attributed to Sn-135. In total, six new levels were identified in Sn-134 on the basis of the beta.. coincidences observed in the In-134 and In-135 beta decays. A transition that might be a candidate for deexciting the missing neutron single-particle 13/2(+) state in Sn-133 was observed in both beta decays and its assignment is discussed. Experimental level schemes of Sn-134 and Sn-135 are compared with shell-model predictions. Using the fast timing technique, half-lives of the 2(+), 4(+), and 6(+) levels in Sn-134 were determined. From the lifetime of the 4(+) state measured for the first time, an unexpectedly large B(E2; 4(+)-> 2(+)) transition strength was deduced, which is not reproduced by the shell-model calculations.Peer reviewe

    Shape coexistence studied in 182,184^182,184 Hg via the β decay of 182,184^182,184 Tl

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    The beta+beta ^+ /EC decay 182,184^182,184 Tl to excited states in the daughter nuclei 182,184^182,184 Hg has been investigated at the CERN on-line isotope mass separator facility. In both Tl nuclei two β -decaying states were observed. In the case of 184 Tl, narrow-band laser spectroscopy could be used to disentangle the decay of both isomers. In 182 Hg a precise energy of 335 (1) keV for the 02+0_2^+ state was measured together with its feeding from a tentatively proposed 23+2_3^+ state at 973 keV. Large conversion coefficients for the 22+to21+2_2^+to 2_1^+ transition in 182,184^182,184 Hg were measured to be 7.2 (13) and 14.2 (36), respectively, evidencing a strong E0 component

    New ß-decaying state in 214Bi

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    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.peerReviewe

    New ß-decaying state in 214Bi

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    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.peerReviewe

    Detailed structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Sn</mml:mi><mml:mprescripts/><mml:none/><mml:mn>131</mml:mn></mml:mmultiscripts></mml:math> populated in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> decay of isomerically purified <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>In</mml:mi><mml:mprescripts/><mml:none/><mml:mn>131</mml:mn></mml:mmultiscripts></mml:math> states

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    The excited structure of the single-hole nucleus Sn131 populated by the β− decay of In131 was investigated in detail at the ISOLDE facility at CERN. This new experiment took advantage of isomeric purification capabilities provided by resonant ionization, making it possible to independently study the decay of each isomer for the first time. The position of the first-excited νh11/2 neutron-hole state was confirmed via an independent mass spectroscopy experiment performed at the Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. The level scheme of Sn131 was notably expanded with the addition of 31 new γ-ray transitions and 22 new excited levels. The γ-emitting excited levels above the neutron separation energy in Sn131 were investigated, revealing a large number of states, which in some cases decay by transitions to other neutron-unbound states. Our analysis showed the dependence between the population of these states in Sn131 and the β-decaying In131 state feeding them. Profiting from the isomer selectivity, it was possible to estimate the direct β feeding to the 3/2+ ground and 11/2− isomeric states, disentangling the contributions from the three indium parent states. This made possible to resolve the discrepancies in logft for first-forbidden transitions observed in previous studies, and to determine the β-delayed neutron decay probability (Pn) values of each indium isomers independently. The first measurement of subnanosecond lifetimes in Sn131 was performed in this work. A short T1/2=18(4)−ps value was measured for the 1/2+ neutron single-hole 332-keV state, which indicates an enhanced l-forbidden M1 behavior for the ν3s1/2−1→ν3d3/2−1 transition. The measured half-lives of high-energy states populated in the β decay of the (21/2+) second isomeric state (In131m2) provided valuable information on transition rates, supporting the interpretation of these levels as core-excited states analogous to those observed in the doubly-magic Sn132. Published by the American Physical Society 2024 </jats:sec

    β-delayed fission and α decay of 178Tl

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    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
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