0000000000962496
AUTHOR
Zs. Podolyák
showing 97 related works from this author
Three beta-decaying states in 128In and 130In resolved for the first time using Penning-trap techniques
2020
Isomeric states in 128In and 130In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in 128In and 130In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the isomer in 128Sn has been discovered in 128In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16⁺ spin-trap isomer. In 130In, the lowest-lying (10⁻) isom…
Spectroscopy of nuclei approaching the proton drip-line using a secondary-fragmentation technique with the RISING detector array
2005
An experiment utilizing a double fragmentation reaction was performed to study isobaric analogue states in A similar to 50 nuclei approaching the proton drip-line. gamma-ray spectroscopy will be used to identify excited states in the neutron-deficient nuclei produced in the second fragmentation reaction. Excited state level schemes will be obtained, through comparison with states in their well-known mirror partners, along with information on Coulomb effects through measurements of the Coulomb energy differences between isobaric analogue excited states. The validity of isospin symmetry for nuclei approaching the proton drip-line can also be investigated and the information gained will aid in…
β−-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes
2009
The low-lying structure of W-188,W-190,W-192 has been studied following beta decays of the neutron-rich mother nuclei Ta-188,Ta-190,Ta-192 produced following the projectile fragmentation of a 1-GeV-per-nucleon Pb-208 primary beam on a natural beryllium target at the GSI Fragment Separator. The beta-decay half-lives of Ta-188, Ta-190, and Ta-192 have been measured, with gamma-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion beta-gamma correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in W-188, W-190, and W-192, which highlight a change in nuclear shape at W-190 compared with that of …
First Measurement of Severalβ-Delayed Neutron Emitting Isotopes BeyondN=126
2016
The β-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N≳126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.
Isomers and high-spin structures in the N=81 isotones Xe135 and Ba137
2017
The high-spin structures of the N = 81 isotones 135Xe and 137Ba are investigated after multinucleontransfer (MNT) and fusion-evaporation reactions. Both nuclei are populated in (i) 136Xe+238U and (ii) 136Xe+208Pb MNT reactions employing the high-resolution Advanced Gamma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA, (iii), in the 136Xe+198Pt MNT reaction employing the -ray array GAMMASPHERE in combination with the gas detector array Chico, and (iv) via a 11B+130Te fusion-evaporation reaction. The high-spin level schemes of 135Xe and 137Ba are considerably extended to higher energies. The 2058-keV (19=2 ) state in 135Xe is identified as an isomer, completing the systema…
A time-of-flight correction procedure for fast-timing data of recoils with varying implantation positions at a spectrometer focal plane
2019
Abstract Fast-timing measurements at the focal plane of a separator can suffer from poor timing resolution. This is due to the variations in time-of-flight (ToF) for photons travelling to a given detector, which arise from the changes in the implantation positions of the recoil nuclei emitting the γ rays of interest. In order to minimise these effects on timing measurements, a procedure is presented that improves fast-timing data by performing ToF corrections on an event-by-event basis. This method was used to correct data collected with an array of eight LaBr 3 detectors, which detected γ rays from spatially distributed 138Gd recoil-implants at the focal plane of the Recoil-Ion-Transport-U…
Role of the Δ Resonance in the Population of a Four-Nucleon State in the Fe56→Fe54 Reaction at Relativistic Energies
2016
The 54Fe nucleus was populated from a 56Fe beam impinging on a Be target with an energy of E=A ¼ 500 MeV. The internal decay via γ-ray emission of the 10þ metastable state was observed. As the structure of this isomeric state has to involve at least four unpaired nucleons, it cannot be populated in a simple two-neutron removal reaction from the 56Fe ground state. The isomeric state was produced in the low-momentum (-energy) tail of the parallel momentum (energy) distribution of 54Fe, suggesting that it was populated via the decay of the Δ0 resonance into a proton. This process allows the population of fournucleon states, such as the observed isomer. Therefore, it is concluded that the obser…
NUCLEAR STRUCTURE ADDRESSED AT GSI/RISING
2009
Nuclear structure spectroscopy studies at GSI recently gained increased momentum within a broad international community with the installation of the Rare Isotopes Spectroscopic INvestigation at GSI (RISING) project. A wide range of physical phenomena has been addressed by high-resolution in-beam γ-ray spectroscopy experiments with radioactive beams. Relativistic radioactive beams are implanted and their subsequent γ and β decay is investigated. Within this "stopped beam campaign" germanium detectors were arranged in a close geometry around the passive stopper or an array of DSSSD detectors. The exceptionally high γ-ray efficiency of that configuration made it possible to identify decays of…
Approaching the precursor nuclei of the third r-process peak with RIBs
2013
The rapid neutron nucleosynthesis process involves an enormous amount of very exotic neutron-rich nuclei, which represent a theoretical and experimental challenge. Two of the main decay properties that affect the final abundance distribution the most are half-lives and neutron branching ratios. Using fragmentation of a primary $^{238}$U beam at GSI we were able to measure such properties for several neutron-rich nuclei from $^{208}$Hg to $^{218}$Pb. This contribution provides a short update on the status of the data analysis of this experiment, together with a compilation of the latest results published in this mass region, both experimental and theoretical. The impact of the uncertainties …
Strong γ-ray emission from neutron unbound states populated in β-decay: Impact on (n,γ) cross-section estimates
2017
J. L. Taín et al. -- 6 pags., 7 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0
Identification of a millisecond isomeric state inCd81129via the detection of internal conversion and Compton electrons
2014
Abstract The decay of an isomeric state in the neutron-rich nucleus 129 Cd has been observed via the detection of internal conversion and Compton electrons providing first experimental information on excited states in this nucleus. The isomer was populated in the projectile fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. From the measured yields of γ -rays and internal conversion electrons, a multipolarity of E 3 was tentatively assigned to the isomeric transition. A half-life of T 1 / 2 = 3.6 ( 2 ) ms was determined for the new state which was assigned a spin of ( 21 / 2 + ) , based on a comparison to shell model calculations performed using state-of-the-art reali…
Investigation of the Δn = 0 selection rule in Gamow-Teller transitions: The β-decay of 207Hg
2019
5 pags., 3 figs., 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0
Nuclear structure “southeast” ofPb208: Isomeric states inHg208andTl209
2009
The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.
Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations
2015
Volume: 111 Host publication title: WONDER-2015 Host publication sub-title: 4TH INTERNATIONAL WORKSHOP ON NUCLEAR DATA EVALUATION FOR REACTOR APPLICATIONS Isbn(print): 978-2-7598-1970-6 Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. Rb-92,Rb-93 are two fission products of importance in reactor antineutrino spectra and decay heat, but their beta-decay properti…
Lifetime measurements in neutron-rich63,65Co isotopes using the AGATA demonstrator
2013
Lifetimes of the low-lying (11/2-) states in 63,65Co have been measured employing the recoil distance doppler shift method (RDDS) with the AGATA γ-ray array and the PRISMA mass spectrometer. These nuclei were populated via a multinucleon transfer reaction by bombarding a 238U target with a beam of 64Ni. The experimental B(E2) reduced transition probabilities for 63,65Co are well reproduced by large-scale shell-model calculations that predict a constant trend of the B(E2) values up to the N=40 67Co isotope
Gamma/neutron competition above the neutron separation energy in delayed neutron emitters
2014
To study the β-decay properties of some well known delayed neutron emitters an experiment was performed in 2009 at the IGISOL facility (University of Jyvaskyla in Finland) using Total Absorption -ray Spectroscopy (TAGS) technique. The aim of these measurements is to obtain the full β-strength distribution below the neutron separation energy (Sn) and the γ/neutron competition above. This information is a key parameter in nuclear technology applications as well as in nuclear astrophysics and nuclear structure. Preliminary results of the analysis show a significant γ-branching ratio above Sn. © Owned by the authors, published by EDP Sciences, 2014.
Identification of yrast high-Kintrinsic states inOs188
2009
The high-spin structure of the $Z=76$ nucleus $^{188}\mathrm{Os}$ has been studied using the incomplete fusion reaction $^{7}\mathrm{Li}+^{186}\mathrm{W}$. A ${K}^{\ensuremath{\pi}}={10}^{+}$ band has been established up to spin $({24}^{+})$ and its crossing with the ground-state band has been studied. In addition, intrinsic high-$K$ states have been identified and on top of two of them, ${K}^{\ensuremath{\pi}}={7}^{\ensuremath{-}}$ and ${K}^{\ensuremath{\pi}}={10}^{\ensuremath{-}}$, regular bands have been observed. The ${K}^{\ensuremath{\pi}}={16}^{+}$ and ${K}^{\ensuremath{\pi}}={18}^{+}$ states are yrast whereas the ${K}^{\ensuremath{\pi}}={14}^{+}$ level lies only 33 keV above the yras…
Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra
2016
International audience; The accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several s…
β-delayedγ-ray spectroscopy of203,204Au and200−202Pt
2013
The beta decay of five heavy, neutron-rich nuclei, Pt-203,Pt-204 and Ir200-202, has been investigated following relativistic cold fragmentation reactions of lead projectiles using the FRS + RISING setup at GSI. This paper reports on the study of the low-lying states in the decay daughter nuclei Au-203,Au-204 and Pt200-202. The characteristic gamma rays for each nucleus have been determined using beta-delayed gamma-ray spectroscopy. Tentative level schemes, relative intensities, and apparent beta feedings are provided. These data are compared with shell-model calculations, which indicate a substantial contribution to the total beta strength from high-energy first-forbidden beta-decay transit…
Characterization of a neutron-beta counting system with beta-delayed neutron emitters
2016
Abstract A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a self-triggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β–neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on …
Total absorption γ-ray spectroscopy of beta delayed neutron emitters
2013
Preliminary results of the data analysis of the beta decay of 94Rb using a novel - segmented- total absorption spectrometer are shown in this contribution. This result is part of a systematic study of important contributors to the decay heat problem in nuclear reactors. In this particular case the goal is to determine the beta intensity distribution below the neutron separation energy and the gamma/beta competition above.
Octupole states in Tl207 studied through β decay
2020
The β decay of 207Hg into the single-proton-hole nucleus 207Tl has been studied through γ-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the πs−11/2, πd−13/2, and πh−111/2 shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states (s1/2-coupled) are identified and three more states (d3/2-coupled) are tentatively assigned using spin-parity inferences, while further h11/2-coupled states may also have been observed for the first time. Comparisons are made with st…
Shape evolution in116,118Ru: Triaxiality and transition between the O(6) and U(5) dynamical symmetries
2013
${}^{116}\mathrm{Ru}$ and ${}^{118}\mathrm{Ru}$ have been studied via $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin $J=6$ have been constructed. The results have been discussed in terms of the interacting boson model, the algebraic collective model, and total Routhian surfaces. We conclude that the very neutron-rich nuclei still show many features associated with triaxial $\ensuremath{\gamma}$-soft nuclei, represented by the O(6) symmetry, but are approaching a spherical structure, the U(5) symmetry, with increasing neu…
'beta'-decay studies of neutron-rich 'TL', 'PB', and 'BI' isotopes
2014
The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft fur Schwerionenforschung laboratory to investigate the β decay of neutron-rich nuclei just beyond 208Pb. This paper reports on β-delayed γ decays of 211-213Tl, 215Pb, and 215-219Bi de-exciting states in the daughters 211-213Pb, 215Bi, and 215-219Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden β transitions in this mass region is discussed. © 2014 American Physical Society.
Lifetime measurement of neutron-rich even-even molybdenum isotopes
2017
D. Ralet et al. -- 11 pags., 10 figs., 3 tabs.
Lifetime measurements in Ti52,54 to study shell evolution toward N=32
2019
Lifetimes of the excited states in the neutron-rich Ti-52,Ti-54 nuclei, produced in a multinucleon-transfer reaction, were measured by employing the Cologne plunger device and the recoil-distance D ...
Measurement of fission products β decay properties using a total absorption spectrometer
2013
In a nuclear reactor, the decay of fission fragments is at the origin of decay heat and antineutrino flux. These quantities are not well known while they are very important for reactor safety and for our understanding of neutrino physics. One reason for the discrepancies observed in the estimation of the decay heat and antineutrinos flux coming from reactors could be linked with the Pandemonium effect. New measurements have been performed at the JYFL facility of Jyvaskyla with a Total Absorption Spectrometer (TAS) in order to circumvent this effect. An overview of the TAS technique and first results from the 2009 measurement campaign will be presented. © Owned by the authors, published by E…
Multipleβ−decaying states in194Re: Shape evolution in neutron-rich osmium isotopes
2012
decays from heavy, neutron-rich nuclei with A∼190 have been investigated following their production via the relativistic projectile fragmentation of an E/A=1 GeV 208Pb primary beam on a ∼2.5 g/cm2 9Be target. The reaction products were separated and identified using the GSI FRagment Separator (FRS) and stopped in the RISING active stopper. γ decays were observed and correlated with these secondary ions on an event-by-event basis such that γ-ray transitions following from both internal (isomeric) and β decays were recorded. A number of discrete, β-delayed γ-ray transitions associated with β decays from 194Re to excited states in 194Os have been observed, including previously reported decays …
Isomers inPd128andPd126: Evidence for a Robust Shell Closure at the Neutron Magic Number 82 in Exotic Palladium Isotopes
2013
The level structures of the very neutron-rich nuclei $^{128}\mathrm{Pd}$ and $^{126}\mathrm{Pd}$ have been investigated for the first time. In the $r$-process waiting-point nucleus $^{128}\mathrm{Pd}$, a new isomer with a half-life of $5.8(8)\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ is proposed to have a spin and parity of ${8}^{+}$ and is associated with a maximally aligned configuration arising from the ${g}_{9/2}$ proton subshell with seniority $\ensuremath{\upsilon}=2$. For $^{126}\mathrm{Pd}$, two new isomers have been identified with half-lives of 0.33(4) and $0.44(3)\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. The yrast ${2}^{+}$ energy is much higher in $^{128}\mathrm{Pd}$ than in…
Determination of beta-delayed neutron emission probability limits of rhodium isotopes by gamma-ray spectroscopy
2019
9 pags., 5 figs., 5 tabs. -- 27th International Nuclear Physics Conference (INPC2019) 29 July - 2 August 2019, Glasgow, UK
High-spin structures in Xe132 and Xe133 and evidence for isomers along the N=79 isotones
2017
Author(s): Vogt, A; Siciliano, M; Birkenbach, B; Reiter, P; Hadynska-Klȩk, K; Wheldon, C; Valiente-Dobon, JJ; Teruya, E; Yoshinaga, N; Arnswald, K; Bazzacco, D; Blazhev, A; Bracco, A; Bruyneel, B; Chakrawarthy, RS; Chapman, R; Cline, D; Corradi, L; Crespi, FCL; Cromaz, M; De Angelis, G; Eberth, J; Fallon, P; Farnea, E; Fioretto, E; Fransen, C; Freeman, SJ; Fu, B; Gadea, A; Gelletly, W; Giaz, A; Gorgen, A; Gottardo, A; Hayes, AB; Hess, H; Hetzenegger, R; Hirsch, R; Hua, H; John, PR; Jolie, J; Jungclaus, A; Karayonchev, V; Kaya, L; Korten, W; Lee, IY; Leoni, S; Liang, X; Lunardi, S; MacChiavelli, AO; Menegazzo, R; Mengoni, D; Michelagnoli, C; Mijatovic, T; Montagnoli, G; Montanari, D; Muller-…
Dealing with contaminants in Coulomb excitation of radioactive beams
2020
Abstract Data analysis of the Coulomb excitation experiment of the exotic 206Hg nucleus, recently performed at CERN’s HIE-ISOLDE facility, needs to account for the contribution to target excitation due to the strongly-present beam contaminant 130Xe. In this paper, the contamination subtraction procedure is presented.
Tz=−1→0βdecays ofNi54,Fe50,Cr46, andTi42and comparison with mirror(He3,t)measurements
2015
We have studied the β decay of the Tz=−1, f7/2 shell nuclei Ni54, Fe50, Cr46, and Ti42 produced in fragmentation reactions. The proton separation energies in the daughter Tz=0 nuclei are relatively large (≈4–5 MeV) so studies of the γ rays are essential. The experiments were performed at GSI as part of the Stopped-beam campaign with the RISING setup consisting of 15 Euroball Cluster Ge detectors. From the newly obtained high precision β-decay half-lives, excitation energies, and β branching ratios, we were able to extract Fermi and Gamow-Teller transition strengths in these β decays. With these improved results it was possible to compare in detail the Gamow-Teller (GT) transition strengths …
Isospin symmetry in thesdshell: Transition strengths in the neutron-deficientsdshell nucleusAr33
2014
Reduced transition strengths of the deexciting transitions from the first two excited states in 33Ar were measured in a relativistic Coulomb excitation experiment at the GSI Helmholtz center. The radioactive ion beam was produced by fragmentation of a primary 36Ar beam on a 9Be target followed by the selection of the reaction product of interest via the GSI Fragment Separator. The 33Ar beam hit a secondary 197Au target with an energy of approximately 145 MeV/nucleon. An array of high-purity germanium cluster detectors and large-volume BaF2 scintillator detectors were employed for γ -ray spectroscopy at the secondary target position. The Lund-York-Cologne Calorimeter was used to track the ou…
Proton Shell Evolution below Sn132 : First Measurement of Low-Lying β -Emitting Isomers in Ag123,125
2019
The β-delayed γ-ray spectroscopy of neutron-rich 123;125Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN and the long-predicted 1/2¯ β-emitting isomers in 123;125Ag are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2+ and 1/2¯ levels is extended in Ag isotopes up to N = 78, providing a clear signal for the reduction of the Z = 40 subshell gap in Ag towards N = 82. Shellmodel calculations with the state-of-the-art VMU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in 123;125Ag. The tensor force is found to play a crucial role in the evolution of…
FIRST RESULTS WITH THE RISING ACTIVE STOPPER
2008
This paper outlines some of the physics opportunities available with the GSI RISING active stopper and presents preliminary results from an experiment aimed at performing beta-delayed gamma-ray spectroscopic studies in heavy-neutron-rich nuclei produced following the projectile fragmentation of a 1 GeV per nucleon 208 Pb primary beam. The energy response of the silicon active stopping detector for both heavy secondary fragments and beta-particles is demonstrated and preliminary results on the decays of neutron-rich Tantalum ( Ta ) to Tungsten ( W ) isotopes are presented as examples of the potential of this technique to allow new structural studies in hitherto experimentally unreachable he…
Decay of theN=126, Fr213nucleus
2016
gamma rays following the EC/beta(+) and alpha decay of the N = 126, Fr-213 nucleus have been observed at the CERN isotope separator on-line (ISOLDE) facility with the help of gamma-ray and conversion-electron spectroscopy. These gamma rays establish several hitherto unknown excited states in Rn-213. Also, five new a-decay branches from the Fr-213 ground state have been discovered. Shell model calculations have been performed to understand the newly observed states in Rn-213.
Total Absorption Study of Beta Decays Relevant for Nuclear Applications and Nuclear Structure
2014
Abstract An overview is given of our activities related to the study of the beta decay of neutron rich nuclei relevant for nuclear applications. Recent results of the study of the beta decay of 87,88 Br using a new segmented total absorption spectrometer are presented. The measurements were performed at the IGISOL facility using trap-assisted total absorption spectroscopy.
β-Decay Half-Lives of 110 Neutron-Rich Nuclei across theN=82Shell Gap: Implications for the Mechanism and Universality of the AstrophysicalrProcess
2015
The $\ensuremath{\beta}$-decay half-lives of 110 neutron-rich isotopes of the elements from $_{37}\mathrm{Rb}$ to $_{50}\mathrm{Sn}$ were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for $r$-process calculations and reinforce the notion that the second ($A\ensuremath{\approx}130$) and the rare-earth-element ($A\ensuremath{\approx}160$) abundance peaks may result from the freeze-out of an $(n,\ensuremath{\gamma})\ensuremath{\rightleftarrows}(\ensuremath{\gamma},n)$ equilibrium. In such an equilibrium, the new half-lives are important factors determining t…
Quadrupole deformation of Xe-130 measured in a Coulomb-excitation experiment
2020
Physical review / C 102(5), 054304 (2020). doi:10.1103/PhysRevC.102.054304
Electromagnetic transition rates in theN=80nucleus58138Ce
2013
The half-life of the Iπ=6+ yrast state at Ex=2294 keV in 138Ce has been measured as T1/2=880(19) ps using the fast-timing γ-ray coincidence method with a mixed LaBr3(Ce)-HPGe array. The excited states in 138Ce have been populated by the 130Te(12C,4n) fusion-evaporation reaction at an incident beam energy of 56 MeV. The extracted B(E2;61+→41+)=0.101(24) W.u. value is compared with the predictions of truncated basis shell model calculations and with the systematics of the region. This shows an anomalous behavior compared to the neighboring isotonic and isotopic chains. Half-lives for the yrast 5-, 11+ and 14+ states in 138Ce have also been determined in this work.
Evidence of octupole-phonons at high spin in 207Pb
2019
A lifetime measurement of the 19/2 state in Pb has been performed using the Recoil Distance Doppler-Shift (RDDS) method. The nuclei of interest were produced in multi-nucleon transfer reactions induced by a Pb beam impinging on a Mo enriched target. The beam-like nuclei were detected and identified in terms of their atomic mass number in the VAMOS++ spectrometer while the prompt γ rays were detected by the AGATA tracking array. The measured large reduced transition probability B(E3,19/2→13/2)=40(8) W.u. is the first indication of the octupole phonon at high spin in Pb. An analysis in terms of a particle-octupole-vibration coupling model indicates that the measured B(E3) value in Pb is compa…
Half-Life Systematics across theN=126Shell Closure: Role of First-Forbidden Transitions in theβDecay of Heavy Neutron-Rich Nuclei
2014
This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic Pb208. The lifetimes of the 126-neutron shell isotone Pt204 and the neighboring Ir200-202, Pt203, Au204 are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first…
New Beta-delayed Neutron Measurements in the Light-mass Fission Group
2014
A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4π neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for {sup 91}Br, {sup 86}As, {sup 85}As, and {sup 85}Ge nuclei.
The BRIKEN Project: Extensive Measurements of $\beta $-delayed Neutron Emitters for the Astrophysical r Process
2018
An ambitious program to measure decay properties, primarily β-delayed neutron emission probabilities and half-lives, for a significant number of nuclei near or on the path of the rapid neutron capture process, has been launched at the RIKEN Nishina Center. We give here an overview of the status of the project.
Observation of a $\gamma$-decaying millisecond isomeric state in $^{128}$Cd$_{80}$
2017
A. Jungclaus et al. -- 6 pags., 5 figs., 2 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0
Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra Determination
2015
8 pags., 3 figs., 1 tab. ; Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015.
β -decay half-lives and β -delayed neutron emission probabilities for several isotopes of Au, Hg, Tl, Pb, and Bi, beyond N=126
2017
Background: Previous measurements of Beta-delayed neutron emitters comprise around 230 nuclei, spanning from the 8He up to 150La. Apart from 210Tl, with a minuscule branching ratio of 0.07%, no other neutron emitter is measured yet beyond A = 150. Therefore new data are needed, particularly in the heavy mass region around N=126, in order to guide theoretical models and to understand the formation of the third r-process peak at A 195. Purpose: To measure both, Beta-decay half-lives and neutron branching ratios of several neutron-rich Au, Hg, Tl, Pb and Bi isotopes beyond N = 126. Method: Ions of interest are produced by fragmentation of a 238U beam, selected and identifed via the GSI-FRS fra…
1p3/2Proton-Hole State inSn132and the Shell Structure AlongN=82
2014
5 pags. ; 3 figs. ; PACS numbers: 23.40.-s, 21.10.Pc, 27.60.+j, 21.60.Cs ; Taprogge, J., et al.
Structures ofPo201andRn205from EC/β+-decay studies
2010
Several low-lying excited states in {sub 86}{sup 205}Rn{sub 119} and {sub 84}{sup 201}Po{sub 117} were identified for the first time following EC/{beta}{sup +} decay of {sup 205}Fr and {sup 201}At, respectively, using {gamma}-ray and conversion electron spectroscopy at the CERN isotope separator on-line (ISOLDE) facility. The EC/{beta}{sup +} branch from {sup 205}Fr was measured to be 1.5(2)%. The excited states of the daughter nuclei are understood in terms of the odd nucleon coupling to the neighboring even-even core. The neutron single-particle energies of the p{sub 3/2} orbital relative to the f{sub 5/2} ground state in {sup 205}Rn, and the f{sub 5/2} orbital relative to the p{sub 3/2} …
Monopole-Driven Shell Evolution below the Doubly Magic Nucleus Sn132 Explored with the Long-Lived Isomer in Pd126
2014
A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in (126)Pd and is proposed to have a spin and parity of 10(+) with a maximally aligned configuration comprising two neutron holes in the 1h(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, β decay from the long-lived isomer was observed to populate excited states at high spins in (126)Ag. The smaller energy difference between the 10(+) and 7(-) isomers in (126)Pd than in the heavier N=80 isotones can be interpreted as being ascribed to the monopole shift of the 1h(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energ…
Total Absorption Spectroscopy Study ofRb92Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape
2015
The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.
Hindered Gamow-Teller Decay to the Odd-OddN=ZGa62: Absence of Proton-NeutronT=0Condensate inA=62
2014
Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, Jπ=0+ ground state of Ge62 into excited states of the odd-odd N=Z nucleus Ga62. The experiment is performed at GSI Helmholtzzentrum fur Schwerionenforschung with the Ge62 ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14) ms is measured for the Ge62 ground state. Six excited states of Ga62, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical pred…
Isospin dependence of electromagnetic transition strengths among an isobaric triplet
2019
*Aydın, Sezgin ( Aksaray, Yazar )
Competition between Allowed and First-Forbidden β Decay: The Case of Hg208→Tl208
2020
The β decay of ^{208}Hg into the one-proton hole, one neutron-particle _{81}^{208}Tl_{127} nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Q_{β} window, only three negative parity states are populated directly in the β decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden β decays, essential for the understanding of the nucleosynthesis of heavy nuclei in…
New isomers in $^{125}$Pd$_{79}$ and $^{127}$Pd$_{81}$: Competing proton and neutron excitations in neutron-rich palladium nuclides towards the $N = …
2019
The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N=82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in Pd and Pd studied using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2 ) and (19/2 ) in Pd and Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitation…
Precision Lifetime Measurements Using LaBr3 Detectors With Stable and Radioactive Beams
2013
A range of high resolution gamma-ray spectroscopy measurements have been carried out using arrays which include a number of Cerium-doped Lanthanum-Tribromide (LrBr3 (Ce)) scintillation detectors used in conjunction with high-resolution hyper-pure germanium detectors. Examples of the spectral and temporal responses of such set-ups, using both standard point radioactive sources 152 Eu and 56 Co, and in-beam fusionevaporation reaction experiments for precision measurements of nuclear excited states in 34 P and 138 Ce are presented. The current and future use of such arrays at existing (EURICA at RIKEN) and future (NUSTAR at FAIR) secondary radioactive beam facilities for precision measurements…
Superallowed Gamow-Teller decay of the doubly magic nucleus $^{100}$Sn
2012
Expérience au GSI; The shell structure of atomic nuclei is associated with 'magic numbers' and originates in the nearly independent motion of neutrons and protons in a mean potential generated by all nucleons. During b1-decay, a proton transforms into a neutron in a previously not fully occupied orbital, emitting a positron-neutrino pair with either parallel or antiparallel spins, in a Gamow-Teller or Fermi transition, respectively. The transition probability, or strength, of a Gamow-Teller transition depends sensitively on the underlying shell structure and is usually distributed among many states in the neighbouring nucleus. Here we report measurements of the half-life and decay energy fo…
Isomeric decay spectroscopy of theBi217isotope
2014
The structure of the neutron-rich bismuth isotope 217Bi has been studied for the first time. The fragmentation of a primary 238U beam at the FRS-RISING setup at GSI was exploited to perform γ-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t1/2=3 μs isomer were observed, allowing one to establish the low-lying structure of 217Bi. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.
Electromagnetic Transition Rate Measurements in theN=80 Isotone,138Ce
2012
A study of intrinsic state halflife measurements in the N=80 nucleus 138Ce has been made using the 130Te(12C,4n)138Ce fusion evaporation reaction at beam energy of 56 MeV. The fast-timing gamma-ray coincidence method was used with a mixed LaBr3(Ce)-HPGe array to establish the lifetimes of the yrast 6+ state at 2294 keV, the Iπ=5− state at 2218 keV, the Iπ=11+ state at 3943 keV and the 14+ state at that at 5312 keV, all of which are in the sub nanosecond regime. Reduced transition probabilities have been calculated for the electromagnetic decays from these states.
Gamow–Teller transitions in exotic pf-shell nuclei relevant to supernova explosion
2007
Gamow–Teller (GT) transitions starting from unstable pf-shell nuclei are of interest not only in nuclear physics, but also in astrophysics, e.g. in violent neutrino induced reactions at the core-collapse stage of type II supernovae. In the β-decay study of these pf-shell nuclei, half-lives can be measured rather accurately. On the other hand, in high-resolution (3He, t) charge-exchange reactions at 0°, individual GT transitions up to high excitations can be studied. Assuming the isospin symmetry for the strengths of Tz = ±1 → 0 analogous GT transitions, we present a unique 'merged analysis' for the determination of absolute B(GT) values.
Relativistic Coulomb excitation of Kr 88
2016
International audience; To investigate the systematics of mixed-symmetry states in N=52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum für Schwerionenforschung to determine E2 transition strengths to 2+ states of the radioactive nucleus $^{88}$Kr. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M1 transition to the fully symmetric 21+ state, extending the knowledge of the N=52 isotones below Z=40. A comparison with the proton-neutron interacting boson model and shell-model predictio…
β-delayed neutron emission measurements around the third r-process abundance peak
2013
This contribution summarizes an experiment performed at GSI (Germany) in the neutron-rich region beyond N=126. The aim of this measurement is to provide the nuclear physics input of relevance for r-process model calculations, aiming at a better understanding of the third r-process abundance peak. Many exotic nuclei were measured around 211Hg and 215Tl. Final ion identification diagrams are given in this contribution. For most of them, we expect to derive halflives and and β-delayed neutron emission probabilities. The detectors used in this experiment were the Silicon IMplantation and Beta Absorber (SIMBA) detector, based on an array of highly segmented silicon detectors, and the BEta deLayE…
Population of lead isotopes in binary reactions using a Rb 94 radioactive beam
2020
8 pags., 9 figs.
Enhancedγ-Ray Emission from Neutron Unbound States Populated inβDecay
2015
Total absorption spectroscopy is used to investigate the β-decay intensity to states above the neutron separation energy followed by γ-ray emission in (87,88)Br and (94)Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For (87)Br and (88)Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daug…
New μs Isomers in the Neutron-rich 210Hg Nucleus
2013
Neutron-rich nuclei in the lead region, beyond N = 126, have been studied at the FRS-RISING setup at GSI, exploiting the fragmentation of a primary uranium beam. Two isomeric states have been identified in Hg-210: the 8(+) isomer expected from the seniority scheme in the vg(9/2) shell and a second one at low spin and low excitation energy. The decay strength of the 8(+) isomer confirms the need of effective three-body forces in the case of neutron-rich lead isotopes. The other unexpected low-lying isomer has been tentatively assigned as a 3(-) state, although this is in contrast with theoretical expectations. (C) 2013 Elsevier B.V. All rights reserved.
First experiment with the NUSTAR/FAIR Decay Total Absorption γ-Ray Spectrometer (DTAS) at the IGISOL IV facility
2015
V. Guadilla et al. ; 4 págs.; 4 figs.; 1 tab.
High-spin structure of Xe134
2016
A. Vogt et al. ; 12 págs.; 9 figs.; 1 tab.
In-beam γ -ray spectroscopy of the neutron-rich platinum isotope Pt200 toward the N=126 shell gap
2017
The neutron-rich nucleus \nucleus{200}{Pt} is investigated via in-beam \gamma-ray spectroscopy in order to study the shape evolution in the neutron-rich platinum isotopes towards the N = 126 shell closure. The two-neutron transfer reaction \nucleus{198}{Pt}(\nucleus{82}{Se}, \nucleus{80}{Se})\nucleus{200}{Pt} is used to populate excited states of \nucleus{200}{Pt}. The Advanced Gamma Ray Tracking Array (AGATA) demonstrator coupled with the PRISMA spectrometer detects \gamma rays coincident with the \nucleus{80}{Se} recoils, the binary partner of \nucleus{200}{Pt}. The binary partner method is applied to extract the \gamma-ray transitions and build the level scheme of \nucleus{200}{Pt}. The …
β-decay and β-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis
2014
New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and β-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them (208-211Hg, 211-215Tl, 214-218Pb) were implanted with enough statistics to determine their half-lives. About half of them a…
Low-lying electric dipole gamma-continuum for the unstable Fe-62,64 nuclei : Strength evolution with neutron number
2020
6 pags., 4 figs.
First Exploration of Neutron Shell Structure below Lead and beyond N=126
2020
The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical r process in producing nuclei heavier than A∼190. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ^{207}Hg have been probed using the neutron-adding (d,p) reaction in inverse kinematics. The radioactive beam of ^{206}Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ^{207}Hg marks a first step in improving our…
Search for very long-lived isomers in the hafnium-tungsten region
2000
Targets of ${}^{48}\mathrm{Ca}$ have been bombarded with ${}^{134,136}\mathrm{Xe}$ beams as part of a search for long-lived, high-K states in well-deformed nuclei with $A\ensuremath{\approx}180.$ Several known isomers were observed by off-line \ensuremath{\gamma}-ray detection, and limits have been established for high-K isomer production in various isotopes of hafnium $(A=175--178),$ tantalum $(A=177--181),$ and tungsten $(A=177--181).$
Study of isomeric states in $^{198,200,202,206}$Pb and $^{206}$Hg populated in fragmentation reactions
2018
International audience; Isomeric states in isotopes in the vicinity of doubly-magic 208Pb were populatedfollowing reactions of a relativistic 208Pb primary beam impinging on a9Be fragmentation target. Secondary beams of 198,200,202,206Pb and 206Hg wereisotopically separated and implanted in a passive stopper positioned in thefocal plane of the GSI Fragment Separator. Delayed γ rays were detected withthe Advanced Gamma Tracking Array (AGATA). Decay schemes were reevaluatedand interpreted with shell-model calculations. The momentumdependentpopulation of isomeric states in the two-nucleon hole nuclei206Pb/206Hg was found to differ from the population of multi neutron-holeisomeric states in 198…
Impact of shell evolution on Gamow-Teller β decay from a high-spin long-lived isomer in 127Ag
2021
6 pags., 4 figs., 2 tabs.
Total absorption spectroscopy study of the β decay of Br86 and Rb91
2017
The beta decays of 86Br and 91Rb have been studied using the total absorption spectroscopy technique. The radioactive nuclei were produced at the IGISOL facility in Jyvaskyla and further purified using the JYFLTRAP. 86Br and 91Rb are considered high priority contributors to the decay heat in reactors. In addition 91Rb was used as a normalization point in direct measurements of mean gamma energies released in the beta decay of fission products by Rudstam et al. assuming that this decay was well known from high-resolution measurements. Our results shows that both decays were suffering from the Pandemonium effect and that the results of Rudstam et al. should be renormalized.
Application of ultra-fast timing techniques to the study of exotic and weakly produced nuclei
2005
Ultra-fast time-delayed techniques have been recently applied in a number of studies where exotic nuclei were identified using advanced selection techniques. These include large Compton-suppressed Ge arrays, in-flight separators or recoil separators. Some of the new results are discussed in this presentation. Besides the results for $^{32}$Mg and $^{96}$Pd, they include the first determination of the half-life of the $8^+$ state in $^{80}$Ge, $T_1/2$ = 2.95(6) ns, and significantly more precise results for $^{51}$Mn (3680 keV level) and $^{48}$V (421 keV level), $T_1/2$ = 1760(40) ps and $T_1/2$ $\leq$ 135 ps, respectively. Development of new scintillators will steadily improve precision an…
High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure
2018
The transitional nucleus 131Xe is investigated after multinucleon transfer (MNT) in the 136Xe+208Pb and 136Xe+238U reactions employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy and as an elusive reaction product in the fusion-evaporation reaction 124Sn(11B,p3n) 131Xe employing the HORUS γ-ray array coupled to a double-sided silicon strip detector (DSSSD) at the University of Cologne, Germany. The level scheme of 131Xe is extended to 5 MeV. A pronounced backbending is observed at ~ω ≈ 0.4 MeV along the negative-parity one-quasiparticle νh11/2(α = −1/2) band. The results are compared to t…
AGATA-Advanced GAmma Tracking Array
2012
WOS: 000300864200005
Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru88
2020
The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N = Z) nuclide 88 44Ru44 has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in 88Ru were populated via the 54Fe(36Ar; 2n )88Ru fusion-evaporation reaction at the Grand Acc�el�erateur National d'Ions Lourds (GANIL) accelerator complex. The observed -ray cascade is assigned to 88Ru using clean prompt - -2-neutron coincidences in anti-coincidence with the detection of charged particles, con�rming and extending the previously assigned sequence of low-lyin…
Investigation of the Δn = 0 selection rule in Gamow-Teller transitions : The β-decay of 207Hg
2019
Gamow-Teller β decay is forbidden if the number of nodes in the radial wave functions of the initial and final states is different. This Δn = 0 requirement plays a major role in the β decay of heavy neutron-rich nuclei, affecting the nucleosynthesis through the increased half-lives of nuclei on the astrophysical r-process pathway below both Z = 50 (for N > 82) and Z = 82 (for N >126). The level of forbiddenness of the Δn = 1ν1g9/2 → π0g7/2 transition has been investigated from the β− decay of the ground state of 207Hg into the single-proton-hole nucleus 207Tl in an experiment at the ISOLDE Decay Station. From statistical observational limits on possible γ-ray transitions depopulating the π0…
Characterization of a neutron–beta counting system with beta-delayed neutron emitters
2016
A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a selftriggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β-neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on the accura…
Decay studies of the long-lived states in $^{186}$Tl
2020
Decay spectroscopy of the long-lived states in $^{186}$Tl has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The $\alpha$ decay from the low-spin $(2^-)$ state in $^{186}$Tl was observed for the first time and a half-life of $3.4^{+0.5}_{-0.4}$ s was determined. Based on the $\alpha$-decay energy, the relative positions of the long-lived states were fixed, with the $(2^-)$ state as the ground state, the $7^{(+)}$ state at 77(56)~keV and the $10^{(-)}$ state at 451(56) keV. The level scheme of the internal decay of the $^{186}$Tl($10^{(-)}$) state ($T_{1/2} = 3.40(9)$ s), which was known to decay solely through emission of 374 keV $\gamma$-ray transition, was extended and a lowe…
β-Delayed and isomer spectroscopy of neutron-rich Ta and W isotopes
2009
Decays of neutron-rich A ~ 190 nuclei have been studied following projectile fragmentation of a 208Pb beam on a 9Be target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in 188Ta, 190W and 192, 193Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in 189Ta and 191W. The current work also identifies β-delayed γ rays following the decay of 188Ta to 188W for the first time. Algora, Alejandro, Alejandro.Algora@ific.uv.es ; Molina Palacios, Francisco Manuel, Francisco.Molina@ific.uv.es; Rubio Barroso, Berta, Berta.Rubio@ific.uv.es
Nature of seniority symmetry breaking in the semimagic nucleus $^{94}Ru$
2022
Physical review / C 105(3), L031304 (2022). doi:10.1103/PhysRevC.105.L031304
Reinvestigation of the excited states in the proton emitter $^{151}$Lu: particle-hole excitations across the $N=Z=64$ subshell
2017
The excited states of the proton emitter $^{151}$Lu were reinvestigated in a recoil-decay tagging experiment at the Accelerator Laboratory of the University of Jyv\"askyl\"a (JYFL). The level scheme built on the ground state of $^{151}$Lu was updated with five new $\gamma$-ray transitions. Large-scale shell model calculations were carried out to interpret the experimental level scheme. It is found that the excitation energies of states above the $27/2^-$ and $23/2^+$ isomeric levels can be sensitive to excitations from $g_{7/2}$ and $d_{5/2}$ to single-particle orbitals above $N=Z=64$.
Competition between allowed and first-forbidden β decays of At208 and expansion of the Po208 level scheme
2021
The structure of 208Po populated through the EC/β+ decay of 208At is investigated using γ-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed γ rays which have been (re)assigned a position. The level scheme is compared to shell model calculations. Through this analysis approximately half of the β-decay strength of 208At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations. This mass r…
Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations
2016
Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland) using Total Absorption Spectroscopy (TAS). TAS is complemen…
Decay studies of the long-lived states in Tl186
2020
Decay spectroscopy of the long-lived states in 186Tl has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The α decay from the low-spin (2−) state in 186Tl was observed for the first time and a half-life of 3.4+0.5−0.4 s was determined. Based on the α-decay energy, the relative positions of the long-lived states were fixed, with the (2−) state as the ground state, the 7(+) state at 77(56) keV, and the 10(−) state at 451(56) keV. The level scheme of the internal decay of the 186Tl(10(−)) state [T1/2=3.40(9) s], which was known to decay solely through emission of 374-keV γ-ray transition, was extended and a lower limit for the β-decay branching bβ>5.9(3)% was determined. The extrac…
Beta-delayed neutron spectroscopy of $^{133}$In
2023
The decay properties of In133 were studied in detail at the ISOLDE Decay Station. The implementation of the Resonance Ionization Laser Ion Source allowed separate measurements of its 9/2+ ground state (In133g) and 1/2− isomer (In133m). With the use of β-delayed neutron and γ spectroscopy, the decay strengths above the neutron separation energy were quantified in this neutron-rich nucleus for the first time. The allowed Gamow-Teller transition 9/2+→7/2+ was located at 5.93 MeV in the In133g decay with a logft=4.7(1). In addition, several neutron-unbound states were populated at lower excitation energies by the first-forbidden decays of In133g,m. We assigned spins and parities to those neutro…
r Process (n, γ) Rate Constraints from the γ Emission of Neutron Unbound States in β decay
2017
Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γγ emission from neutron-unbound states populated in the ββ-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission a constraint on the (n, γγ) cross section for highly unstable neutron-rich nuclei can be deduced. A surprisingly large γγ branching was observed for a number of isotopes which might indicate the need to increase by a large factor the Hauser-Feshbach (n, γγ) cross-section estimates that impact on r process abundance calculations. peerReviewed
Reinvestigation of the excited states in the proton emitter 151Lu : Particle-hole excitations across the N=Z=64 subshell
2017
The excited states of the proton emitter 151Lu were reinvestigated in a recoil-decay tagging experiment at the Accelerator Laboratory of the University of Jyväskylä (JYFL). The level scheme built on the ground state of 151Lu was updated with five new γ -ray transitions. Large-scale shell model calculations were carried out in the model space consisting of the neutron and proton orbitals 0g7/2, 1d5/2, 1d3/2, 2s1/2, and 0h11/2 with the optimized monopole interaction in order to interpret the experimental level scheme of 151Lu. It is found that the excitation energies of states above the 27/2− and 23/2+ isomeric levels in 151Lu can be sensitive to excitations from g7/2 and d5/2 to single-parti…
Oblate Collectivity in the Yrast Structure of 194Pt
2005
A deep inelastic reaction using a 460 MeV 82Se beam incident upon a thick 192Os target was performed at the Legnaro National Laboratory, Italy. The resulting γ-decays were measured using the GASP array. Results for 194Pt extend the known level scheme of the yrast structure from spin I = (12 ħ) to (20 ħ). The irregularities in the sequence of the new transition energies and total Routhian surface calculations show a breakdown in collectivity with an yrast oblate shape remaining to high spin. Rubio Barroso, Berta, Berta.Rubio@ific.uv.es
Competition between Allowed and First-Forbidden β Decay : The Case of Hg208→Tl208
2020
The β decay of 208Hg into the one-proton hole, one neutron-particle 20881Tl127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Qβ window, only three negative parity states are populated directly in the β decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden β decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neut…
First Exploration of Neutron Shell Structure Below Lead and Beyond $\boldsymbol{N=126}$
2020
The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical $r$-process in producing nuclei heavier than $A\sim190$. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in $^{207}$Hg have been probed using the neutron-adding ($d$,$p$) reaction in inverse kinematics. The radioactive beam of $^{206}$Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of $^{207}$Hg marks a first step…
Quadrupole and octupole collectivity in the semi-magic nucleus 80,206Hg126
2023
The first low-energy Coulomb-excitation measurement of the radioactive, semi-magic, two proton-hole nucleus 206Hg, was performed at CERN’s recently-commissioned HIE-ISOLDE facility. Two γ rays depopulating low-lying states in 206Hg were observed. From the data, a reduced transition strength B(E2; 2+ 1 → 0+ 1 ) = 4.4(6) W.u was determined, the first such value for an N = 126 nucleus south of 208Pb, which is found to be slightly lower than that predicted by shell-model calculations. In addition, a collective octupole state was identified at an excitation energy of 2705 keV, for which a reduced B(E3) transition probability of 30+10−13 W.u was extracted. These results are crucial for understand…
Three beta-decaying states in In and In resolved for the first time using Penning-trap techniques
2020
Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in $^{128}$In and $^{130}$In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the 15− isomer in $^{128}$Sn has been discovered in $^{128}$In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16+ spin-trap isomer. In …