Search results for "nuclear structure"

Identification of a 6.6μs isomeric state in 175Ir

2019

An experiment has been performed to study excited states in the neutron-deficient nucleus 175Ir via the use of the JUROGAM II high-purity germanium detector array and the RITU gas-filled separator at JYFL, Jyväskylä. By using isomer tagging, an isomeric state with a half-life of 6.58(15) μs has been observed in 175Ir for the first time. It has been established that the isomer decays via a 45.2 (E1)–26.1 (M1) keV cascade to new states below the previously reported ground state in 175Ir with Iπ = (5/2−). We now reassign this (5/2−) state to the isomeric state discovered in this study. peerReviewed

Exploring the boundaries of the nuclear landscape : α-decay properties of 211Pa

2020

Employing the recoil ion transport unit (RITU) and a fusion-evaporation reaction, the α decay of 211Pa has been identified via the implantation-decay correlation technique through observation of chains up to four consecutive decays. An α-particle energy and half-life of 8320(40) keV and 3.8+4.6−1.4 ms, respectively, were measured, corresponding to favored α decay. In addition, more precise α-decay properties of 212Pa and 213Pa were obtained due to accumulated statistics. The present data were compared to those predicted by selected atomic mass models and it was used to estimate the possibility of observing proton emission from these isotopes. peerReviewed

First evidence of multiple β-delayed neutron emission for isotopes with a > 100

2017

The β-delayed neutron emission probability, Pn, of very neutron-rich nuclei allows us to achieve a better understanding of the nuclear structure above the neutron separation energy, Sn. The emission of neutrons can become the dominant decay process in neutron-rich astrophysical phenomena such as the rapid neutron capture process (r-process). There are around 600 accessible isotopes for which β-delayed one-neutron emission (β1n) is energetically allowed, but the branching ratio has only been determined for about one third of them. β1n decays have been experimentally measured up to the mass A ∼ 150, plus a single measurement of 210Tl. Concerning two-neutron emitters (β2n), ∼ 300 isotopes are …

Shape staggering of midshell mercury isotopes from in-source laser spectroscopy compared with density-functional-theory and Monte Carlo shell-model c…

2019

Neutron-deficient Hg177-185 isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility in an experiment combining different detection methods tailored to the studied isotopes. These include either α-decay tagging or multireflection time-of-flight gating for isotope identification. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring for the first time the isotope shifts and hyperfine structures of Hg177-180. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole, and electric quadrupole moments of the odd-A isotopes and arguments in favor of I=7/2 s…

Correlating Schiff Moments in the Light Actinides with Octupole Moments

2018

Determination of β-decay ground state feeding of nuclei of importance for reactor applications

2020

In β-decay studies the determination of the decay probability to the ground state (g.s.) of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed γ-ray emission. In this work we revisit the 4πγ−β method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the β-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large g.s. branches. The method is…

Spectroscopy of 70Kr and isospin symmetry in the T = 1 f pg shell nuclei

2016

International audience; The recoil-β tagging technique has been used in conjunction with the 40 Ca(32 S ,2n) reaction at a beam energy of 88 MeV to identify transitions associated with the decay of the 2 + and, tentatively, 4 + states in the nucleus 70 Kr. These data are used, along with previously published data, to examine the triplet energy differences (TED) for the mass 70 isobars. The experimental TED values are compared with shell model calculations, performed with the JUN45 interaction in the fpg model space, that include a J = 0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV. The agreement is found to be very good up to spin 4 and supports the expectat…

Penning-trap mass measurements on 92, 94-98, 100Mo with JYFLTRAP

2012

Penning-trap measurements on stable 92, 94-98, 100Mo isotopes have been performed with relative accuracy of \ensuremath1⋅10−8\ensuremath1⋅10−8 with the JYFLTRAP Penning-trap mass spectrometer by using 85Rb as a reference. The Mo isotopes have been found to be about 3keV more bound than given in the Atomic Mass Evaluation 2003 (AME03). The results confirm that the discrepancy between the ISOLTRAP and JYFLTRAP data for 101-105Cd isotopes was due to an erroneous value in the AME03 for 96Mo used as a reference at JYFLTRAP. The measured frequency ratios of Mo isotopes have been used to update mass-excess values of 30 neutron-deficient nuclides measured at JYFLTRAP. peerReviewed

Mass measurements of neutron-deficient nuclei and their implications for astrophysics

2012

During the years 2005-2010 the double-Penning-trap mass spectrometer JYFLTRAP has been used to measure the masses of 90 ground and 8 isomeric states of neutron-deficient nuclides with a typical precision of better than 10keV. The masses of 14 nuclides -- 84Zr , 88, 89Tc , 90-92Ru , 92-94Rh , 94, 95Pd , 106, 108, 110Sb -- have been experimentally determined for the first time. This article gives an overview on these measurements and their impact on the modeling of the astrophysical rp -process. peerReviewed

Underground multi-muon experiment EMMA

2011

EMMA is a new experiment designed for cosmic-ray composition studies around the knee energy operating at the shallow depth underground in the Pyhäsalmi mine, Finland. The array has sufficient coverage and resolution to determine the multiplicity, the lateral density distribution and the arrival direction of high-energy muons on an event by event basis. Preliminary results on the muon multiplicity extracted using one detector station of the array are presented. peerReviewed