Search

The very proton-rich 71Kr isotope was produced through the in-flight fragmentation of 78Kr on a beryllium target at RIKEN – Nishina Center in order to study its β-decay properties. A stack of double-sided silicon strip detectors, called WAS3ABi, was used as the decay station, where the detection of ion implants, β-decays and β-delayed protons took place. Beta-delayed γ-rays were measured using a system of 84 HPGe detectors, called EURICA, surrounding the decay station. The main goal of the present study was the precise measurement of the half-life of 71Kr, as in the literature there is an almost 10 σ difference between the most precise independent results. Implant–β time correlations, implant–proton time correlations and implant–β–γ time correlations were all used to derive the half-life value, followed by a thorough investigation of systematic uncertainties for each method. As these values were found to be consistent, the weighted average t1/2 = 94.40+19ms is reported as a new half-life value in this work. Furthermore a total of 26 previously unreported γ following the β-decay of 71Kr were also identified in the analysis.

Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars and for applications in nuclear technology. However, their measurement is very complicated due to the radioactivity of the targets involved. We propose to circumvent this problem by using the surrogate reaction method in inverse kinematics, where the nucleus formed in the neutron- induced reaction of interest is produced by a reaction involving a radioactive heavy-ion beam and a stable, light target nucleus. The probabilities as a function of the compound-nucleus excitation energy for γ-ray emission, neutron emission and fission, which can be measured with the surrogate reaction, are particularly useful to constrain model parameters and to obtain more accurate predictions of the neutron-induced reaction cross sections of interest. Yet, the full development of the surrogate method is hampered by numerous long- standing target issues, which can be solved by combining surrogate reactions with the unique and largely unexplored possibilities at heavy-ion storage rings. In this contribution, we describe the developments we are carrying out to measure for the first time simultaneously γ-ray emission, neutron emission and fission probabilities at the storage rings of the GSI/FAIR facility. In particular, we will present the first results of the proof of principle experiment, which we performed in June 2022 at the Experimental Storage Ring (ESR) of GSI/FAIR.

Neutron-induced reaction cross sections of unstable nuclei are essential for understanding the synthesis of heavy elements in stars. However, their measurement is very difficult due to the radioactivity of the targets involved. We propose to circumvent this problem by using for the first time the surrogate reaction method in inverse kinematics at heavy-ion storage rings. In this contribution, we describe the developments we have done to perform surrogate-reaction studies at the storage rings of GSI/FAIR. In particular, we present the first results of the proof of principle experiment, which we conducted recently at the Experimental Storage Ring (ESR).

Remarkable results have been published recently on the β decay of 56Zn. In particular, the rare and exotic β-delayed γ-proton emission has been detected for the first time in the fp shell. Here we focus the discussion on this exotic decay mode and on the observed competition between β-delayed protons and β-delayed γ rays from the Isobaric Analogue State.

The half-life of 14O, a superallowed Fermi β+ emitter, has been determined via simultaneous γ and β counting experiments at TRIUMF’s Isotope Separator and Accelerator facility. Following the implantation of 14O samples at the center of the 8π spectrometer, a γ counting measurement was performed by detecting the 2313 keV γ-rays emitted from the first excited state of the daughter 14N using 20 high-purity germanium (HPGe) detectors. A simultaneous β counting experiment was performed using a fast plastic scintillator positioned directly behind the implantation site. The results, T½(γ) = 70:632 ± 0:094 s and T½(β) = 70:610 ± 0:030 s, are consistent with one another and, together with eight previous measurements, establish a new average for the 14O half-life of T½ = 70:619 ± 0:011 s with a reduced χ2 of 0.99.

The β decay properties of the Tz = -2, 56Zn isotope and other proton-rich nuclei in the fp-shell have been investigated in an experiment performed at GANIL. The ions were produced in fragmentation reactions and implanted in a double-sided silicon strip detector surrounded by Ge EXOGAM clovers. Preliminary results for 56Zn are presented .The 56Zn decay proceeds mainly by β delayed proton emission, but β delayed gamma rays were also detected. Moreover, the exotic β delayed gamma-proton decay was observed for the first time. The 56Zn half-life and the energy levels populated in the 56Cu daughter have been determined. Knowledge of the gamma de-excitation of the mirror states in 56Co and the comparison with the results of the mirror charge exchange process, the 56Fe(3He,t) reaction (where 56Fe has Tz = +2), were important in the interpretation of the 56Zn decay data. The absolute Fermi and Gamow-Teller strengths have been deduced.

A program of high-precision half-life and branching-ratio measurements for superallowed Fermi β emitters is being carried out at TRIUMF’s Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. Recent half-life measurements for the superallowed decays of 14O, 18Ne, and 26Alm, as well as branching-ratio measurements for 26Alm and 74Rb are reported. These results provide demanding tests of the Standard Model and the theoretical isospin symmetry breaking (ISB) corrections in superallowed Fermi β decays.