0000000000118858
AUTHOR
Laetitia Canete
First determination of β-delayed multiple neutron emission beyond A = 100 through direct neutron measurement : The P2n value of 136Sb
Background: β-delayed multiple neutron emission has been observed for some nuclei with A≤100, being the Rb100 the heaviest β2n emitter measured to date. So far, only 25P2n values have been determined for the ≈300 nuclei that may decay in this way. Accordingly, it is of interest to measure P2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A>100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of a…
Precision Mass Measurements on Neutron-Rich Rare-Earth Isotopes at JYFLTRAP : Reduced Neutron Pairing and Implications for r-Process Calculations
The rare-earth peak in the r-process abundance pattern depends sensitively on both the astrophysical conditions and subtle changes in nuclear structure in the region. This work takes an important step towards elucidating the nuclear structure and reducing the uncertainties in r-process calculations via precise atomic mass measurements at the JYFLTRAP double Penning trap. Nd158, Pm160, Sm162, and Gd164-166 have been measured for the first time, and the precisions for Nd156, Pm158, Eu162,163, Gd163, and Tb164 have been improved considerably. Nuclear structure has been probed via two-neutron separation energies S2n and neutron pairing energy metrics Dn. The data do not support the existence of…
Fission studies at IGISOL/JYFLTRAP: Simulations of the ion guide for neutron-induced fission and comparison with experimental data
For the production of exotic nuclei at the IGISOL facility, an ion guide for neutron-induced fission has been developed and tested in experiments. Fission fragments are produced inside the ion guide and collected using a helium buffer gas. Meanwhile, a GEANT4 model has been developed to simulate the transportation and stopping of the charged fission products. In a recent measurement of neutron-induced fission yields, implantation foils were located at different positions in the ion guide. The gamma spectra from these foils and the fission targets are compared to the results from the GEANT4 simulation. In order to allow fission yield measurements in the low yield regions, towards the tails a…
High-Precision Proton-Capture Q Values for 25Al(p,γ)26Si and 30P(p,γ)31Si
The masses of astrophysically relevant nuclei, 25Al and 30P, have recently been measured with the JYFLTRAP double Penning trap at the new IGISOL-4 facility at the University of Jyväskylä. Unparalleled precisions of 63 and 64 eV were achieved for the 25Al and 30P masses, respectively. The proton-capture Q values for 25Al(p, γ)26Si and 30P(p, γ)31S were also determined, and their precisions improved by a factor of 4 and 2, respectively, in comparison with AME12. The impact of the more precise values on the resonant proton-capture rate has also been studied. peerReviewed
High-precision measurement of the mass difference between 102Pd and 102Ru
The Q-value for the neutrinoless double electron capture on 102Pd, Qϵϵ(102Pd), is determined as the atomic mass difference between 102Pd and 102Ru. A precise measurement of the Qϵϵ(102Pd) at the SHIPTRAP Penning trap showed a more than 10σ deviation to the adopted Atomic Mass Evaluation (AME) value. The reliability of the SHIPTRAP measurement was challenged because the AME value was based on numerous experiments including β and electron capture decays and very precise (n, γ) data, all agreeing with each other. To solve the discrepancy, the Qϵϵ(102Pd) has now been determined with the JYFLTRAP Penning trap at the IGISOL facility in the Accelerator Laboratory of the University of Jyväskylä. Th…
β Decay of 127Cd and Excited States in 127In
A dedicated spectroscopic study of the β decay of 127Cd was conducted at the IGISOL facility at the University of Jyväskylä. Following high-resolution mass separation in a Penning trap, β−γ−γcoincidences were used to considerably extend the decay scheme of 127In. The β-decaying 3/2+ and 11/2− states in 127Cd have been identified with the 127Cd ground state and the 283-keV isomer. Their respective half-lives have been measured to 0.45(128)s and 0.36(4) s. The experimentally observed βfeeding to excited states of 127In and the decay scheme of 127In are discussed in conjunction with large-scale shell-model calculations. peerReviewed
Mass Measurements for the rp Process
One of the key parameters for the reaction network calculations for the rapid proton capture (rp) process, occurring e.g., in type I X-ray bursts, are the masses of the involved nuclei. Nowadays, masses of even rather exotic nuclei can be measured very precisely employing Penning-trap mass spectrometry. With the JYFLTRAP Penning trap at the IGISOL facility, masses of around 100 neutron-deficient nuclei have been determined with a typical precision of a few keV. Most recently, 25Al, 30P, 31Cl, and 52Co have been measured. Of these, the precision of the mass-excess value of 31Cl was improved from 50 to 3.4 keV, and the mass of 52Co was experimentally determined for the first time. The mass of…
First evidence of multiple β-delayed neutron emission for isotopes with a > 100
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 …
Precision 71Ga – 71Ge mass-difference measurement
The 71Ga(νe, e−) 71Ge reaction Q value has been measured with the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyv¨askyl¨a to Q = 232.443(93) keV. This value agrees with previous measurements, though it features a much higher accuracy. The Q value is being discussed in the context of the solar neutrino capture rate in 71Ga. peerReviewed
QEC value of the superallowed β emitter 42Sc
The QEC value of the superallowed β+ emitter Sc42 has been measured with the JYFLTRAP Penning-trap mass spectrometer at the University of Jyväskylä to be 6426.350(53) keV. This result is at least a factor of four more precise than all previous measurements, which were also inconsistent with one another. As a byproduct we determine the excitation energy of the 7+ isomeric state in Sc42 to be 616.762(46) keV, which deviates by 8σ from the previous measurement. peerReviewed