Mon·Jun 28, 2021Monday·June 28, 2021

1. 01*

   Isomeric states in neutron-rich nuclei around $N=40$

   K. Wimmer🇯🇵 · F. Recchia🇮🇹 · S. M. Lenzi🇮🇹 · S. Riccetto🇨🇦 · T. Davinson · A. Estrade🇩🇪 · C. J. Griffin · S. Nishimura🇯🇵 · V. Phong🇻🇳 · P.-A. Söderström🇩🇪 · O. Aktas · M. Al-Aqeel and 28 other authors

   Neutron-rich nuclei in the vicinity of the $N=40$ island of inversion are characterized by shell evolution and exhibit deformed ground states. In several nuclei isomeric states have been observed and attributed to excitations to the intruder neutron $1g_{9/2}$ orbital. In the present study we searched for isomeric states in nuclei around $N=40$, $Z=22$ produced by projectile fragmentation at RIBF. Delayed $\gamma$ rays were detected by the EURICA germanium detector array. High statistics data allowed for an updated decay scheme of ${}^{60}$V. The lifetime of an isomeric state in ${}^{64}$V was measured for the first time in the present experiment. A previously unobserved isomeric state was discovered in ${}^{58}$Sc. The measured lifetime suggests a parity changing transition, originating from an odd number of neutrons in the $1g_{9/2}$ orbital. The nature of the isomeric state in ${}^{58}$Sc is thus different from isomers in the less exotic V and Sc nuclei.

   nucl-exPRC(2021)·3 citations
2. 02*

   Delayed ${}^{160}$Tb radioactivity buildup due to ${}^{159}$Tb(n,${}^2$n) nuclear reaction products transformation and subsequent fusion

   Ihor M. Kadenko🇺🇦 · Nadiia V. Sakhno · Oleksandr M. Gorbachenko · Anastasiia V. Synytsia

   This paper deals with the formation of a bound dineutron in the outgoing channel of the ${}^{159}$Tb(n,${}^2$n)${}^{158g}$Tb nuclear reaction followed by assumed transformations of this reaction products ${}^{159g}$Tb and ${}^2$n. Such nuclear processes were studied in detail from the point of view of ${}^{160}$Tb / ${}^{160}$Dy / ${}^{160}$Ho amount of nuclei versus time dependence. Some signs of fusion process between heavier nuclei (${}^{158}$Tb and/or ${}^{158}$Gd) and the deuteron, that is a bound dineutron decay product, were detected as unexpected increasing of 879.38 keV gamma-ray peak count rate due to ${}^{160}$Dy gamma-transitions. The mathematical model, including three systems of differential equations, was developed to describe the experimental data. This development requires a reasonable estimate of the half-life of a bound dineutron, which was found to be equal 5,877 s as an upper limit. We mathematically modeled the experimentally observed delayed in time buildup of the ${}^{160}$Tb radioactivity with a maximum at about 495 d since the neutron irradiation completion of the Tb sample, based on the similarity with the parent-daughter nuclei radioactivity decay and nuclear accumulation processes.

   nucl-exNPA(2023)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.