Search results for "nuclear structure"
showing 10 items of 401 documents
Excited states in 87Br populated in β decay of 87Se
2019
Excited levels in 87Br, populated in β decay of 87Se, have been studied by means of γ-ray spectroscopy using an array of broad energy Ge detectors. 87Se nuclei were produced by irradiating a natural Th target with 25-MeV protons. Fission products were extracted from the target chamber using the IGISOL technique, then separated on a dipole magnet and Penning trap (JYFLTRAP) setup. The scheme of excited levels of 87Br has been significantly extended. 114 new transitions and 51 new levels were established. β feedings and log(ft) values of levels were determined. The upper limit for β feeding to the ground state of 87Br was determined to be 23(5)%. Ground state spin and parity 5/2− was confirme…
β- and γ-spectroscopy study of 119Pd and 119Ag
2022
Neutron-rich 119Pd nuclei were produced in fission of natural uranium, induced by 25-MeV protons. Fission fragments swiftly extracted with the Ion Guide Isotope Separation On-Line method were mass separated using a dipole magnet and a Penning trap, providing mono-isotopic samples of 119Pd. Their β− decay was measured with γγ- and βγ-spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in 119Ag, based on the 1/2− and 7/2+ isomers reported previously. The β−-decay work was complemented by a prompt-γ study of levels in 119Ag populated in spontaneous fission of 252Cf, performed using the Gammasphere array …
Ordinary muon capture studies for the matrix elements in ββ decay
2019
High-purity germanium (HPGe) detectors were used to make a precise measurement of the γ-ray spectrum produced following ordinary (nonradiative) capture of negative muons by natural Se, Kr, Cd, and Sm. The measurement was repeated for isotopically enriched 48Ti, 76Se, 82Kr, 106Cd, and 150Smtargets. By investigating energy and time distributions, the lifetime of negative muons in the different isotopes was deduced. A detailed analysis of the intensity of the γ lines enabled the extraction of the relative yields of several daughter nuclei. The partial rates of (μ−,ν) capture to numerous excited levels of the 48Sc, 76As, 82Br, 106Ag, and 150Tc isotopes (considered to be virtual states of the in…
Improved calculations of beta decay backgrounds to new physics in liquid xenon detectors
2020
We present high-precision theoretical predictions for the electron energy spectra for the ground-state to ground-state $\beta$ decays of $^{214}$Pb, $^{212}$Pb, and $^{85}$Kr most relevant to the background of liquid xenon dark matter detectors. The effects of nuclear structure on the spectral shapes are taken into account using large-scale shell model calculations. Final spectra also include atomic screening and exchange effects. The impact of nuclear structure effects on the $^{214}$Pb and $^{212}$Pb spectra below $\approx100$ keV, pertinent for several searches for new physics, are found to be comparatively larger than those from the atomic effects alone. We find that the full calculatio…
Analysis of light neutrino exchange and short-range mechanisms in 0νββ decay
2020
Neutrinoless double beta decay (0νββ) is a crucial test for lepton number violation. Observation of this process would have fundamental implications for neutrino physics, theories beyond the Standard Model and cosmology. Focusing on so-called short-range operators of 0νββ and their potential interplay with the standard light Majorana neutrino exchange, we present the first complete calculation of the relevant nuclear matrix elements, performed within the interacting boson model (IBM-2). Furthermore, we calculate the relevant phase space factors using exact Dirac electron wave functions, taking into account the finite nuclear size and screening by the electron cloud. The obtained numerical r…
Structure of superheavy nuclei along decay chains of element 115
2014
[Introduction] A recent high-resolution α , X -ray, and γ -ray coincidence-spectroscopy experiment offered the first glimpse of excitation schemes of isotopes along α -decay chains of Z = 115. To understand these observations and to make predictions about shell structure of superheavy nuclei below 288 115, we employ two complementary mean-field models: the self-consistent Skyrme energy density functional approach and the macroscopic-microscopic Nilsson model. We discuss the spectroscopic information carried by the new data. In particular, candidates for the experimentally observed E 1 transitions in 276 Mt are proposed. We find that the presence and nature of low-energy E 1 transitions in w…
Precision mass measurements of 67Fe and 69,70Co: Nuclear structure toward N = 40 and impact on r-process reaction rates
2020
Accurate mass measurements of neutron-rich iron and cobalt isotopes 67Fe and 69,70Co have been realized with the JYFLTRAP double Penning-trap mass spectrometer. With novel ion-manipulation techniques, the masses of the 69,70Co ground states and the 1/2− isomer in 69Co have been extracted for the first time. The measurements remove ambiguities in the previous mass values and yield a smoother trend on the mass surface, extending it beyond N=40. The moderate N=40 subshell gap has been found to weaken below 68Ni, a region known for shape coexistence and increased collectivity. The excitation energy for the 1/2− intruder state in 69Co has been determined for the first time and is compared to lar…
Microscopic structure of coexisting $0^+$ states in $^{68}$Ni probed via two-neutron transfer
2019
© 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)% rela…
Search for Electron-Capture Delayed Fission in the New Isotope 244Md
2020
The electron-capture decay followed by a prompt fission process was searched for in the hitherto unknown most neutron-deficient Md isotope with mass number 244. Alpha decay with α-particle energies of 8.73-8.86 MeV and with a half-life of 0.30_{-0.09}^{+0.19} s was assigned to ^{244}Md. No fission event with a similar half-life potentially originating from spontaneous fissioning of the short-lived electron-capture decay daughter ^{244}Fm was observed, which results in an upper limit of 0.14 for the electron-capture branching of ^{244}Md. Two groups of fission events with half-lives of 0.9_{-0.3}^{+0.6} ms and 5_{-2}^{+3} ms were observed. The 0.9_{-0.3}^{+0.6} ms activity was assigned t…
Quantum-state-selective decay spectroscopy of 213Ra
2017
An experimental scheme combining the mass resolving power of a Penning trap with contemporary decay spectroscopy has been established at GSI Darmstadt. The Universal Linear Accelerator (UNILAC) at GSI Darmstadt provided a 48Ca beam impinging on a thin 170Er target foil. Subsequent to velocity filtering of reaction products in the Separator for Heavy Ion reaction Products (SHIP), the nuclear ground state of the 5n evaporation channel 213Ra was mass-selected in SHIPTRAP, and the 213Ra ions were finally transferred into an array of silicon strip detectors surrounded by large composite germanium detectors. Based on comprehensive geant4 simulations and supported by theoretical calculations, the …