Abstract. The properties of the excited states of gold isotopes were investigated at the Oslo Cyclotron Laboratory. This study is important for the understanding of neutron capture rates in astrophysical plasmas relevant for heavy element nucleosynthesys.
Neutron-rich Pm (Z = 61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, Riken Nishina Center using the in-flight fission of 345MeV/u 238 U beam. An array of cluster-type Ge detectors, EURICA, was used to measure the delayed γ rays from stopped ions.
Nuclear level densities (NLDs) and γ-ray strength functions (GSFs)of 120;124Sn have been extracted with the Oslo method and additionally constrained with the novel Shape method. The GSFs were found to be in excellent agreement with the strengths from the inelastic relativistic proton scattering experiment. This comparison suggests the validity of the Brink-Axel hypothesisused as one of the key assumptions in astrophysical calculations. The extracted NLDs and GSFs were further used as experimental inputs to constrain the Maxwellian-averaged cross sections (MACS) for the radiative neutron capture process 119;123Sn (n, γ)120;124Sn using the the nuclear reaction code TALYS.
A new isomer with µs half-life was observed in 160 Nd at RIBF, RIKEN Nishina Center by using in-flight fission of a 238 U beam and a cluster-type Ge detector array, EURICA. The experimental results and a PSM calculation indicate that the isomer in 160 Nd is a 2 quasi-particle excitation of neutrons with a configuration of ν1/2[521] ⊗ ν7/2[633] as the case in other N = 100 isotones. The E(4 +)/E(2 +) ratio of the ground-state band, 3.29, shows the 160 Nd is well deformed and the ground band has a rotational nature. The 4 − excitation of 160 Nd showed an increase in energy by ∼ 100 keV compared to that of 162 Sm as predicted by the PSM calculation. A PSM calculation was performed by changing input β 4 value and confirmed that the large hexadecupole deformation in Nd was responsible for the increase of the isomer energy.
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