arXiv subjects

Ch. Sotty

Publications and source records attributed to Ch. Sotty.

4 recordsLinked to original sources

arXiv2023

133In: A Rosetta Stone for decays of r-process nuclei

The $β$ decays from both the ground state and a long-lived isomer of $^{133}$In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to $β$, $γ$, and neutron spectroscopy, the comparative partial half-lives (logft) have been measured for all their dominant $β$-decay channels for the first time, including a low-energy Gamow-Teller transition and several First-Forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their $β$ decays selectively populate only a few isolated neutron unbound states in $^{133}$Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark $β$-decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the $β$ decay of neutron-rich nuclei southeast of $^{132}$Sn and will serve as a guide for future theoretical development aiming to describe accurately the key $β$ decays in the rapid-neutron capture (r-) process.

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arXiv2023

Beta-delayed neutron spectroscopy of $^{133}$In

The decay properties of $^{133}$In were studied in detail at the ISOLDE Decay Station (IDS). The implementation of the Resonance Ionization Laser Ion Source (RILIS) allowed separate measurements of its $9/2^+$ ground state ($^{133g}$In) and $1/2^-$ isomer ($^{133m}$In). With the use of $β$-delayed neutron and $γ$ spectroscopy, the decay strengths above the neutron separation energy were quantified in this neutron-rich nucleus for the first time. The allowed Gamow-Teller transition $9/2^+\rightarrow7/2^+$ was located at 5.92 MeV in the $^{133g}$In decay with a logft = 4.7(1). In addition, several neutron-unbound states were populated at lower excitation energies by the First-Forbidden decays of $^{133g,m}$In. We assigned spins and parities to those neutron-unbound states based on the $β$-decay selection rules, the logft values, and systematics.

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arXiv2020

Decay studies of the long-lived states in $^{186}$Tl

Decay spectroscopy of the long-lived states in $^{186}$Tl has been performed at the ISOLDE Decay Station at ISOLDE, CERN. The $α$ decay from the low-spin $(2^-)$ state in $^{186}$Tl was observed for the first time and a half-life of $3.4^{+0.5}_{-0.4}$ s was determined. Based on the $α$-decay energy, the relative positions of the long-lived states were fixed, with the $(2^-)$ state as the ground state, the $7^{(+)}$ state at 77(56)~keV and the $10^{(-)}$ state at 451(56) keV. The level scheme of the internal decay of the $^{186}$Tl($10^{(-)}$) state ($T_{1/2} = 3.40(9)$ s), which was known to decay solely through emission of 374 keV $γ$-ray transition, was extended and a lower-limit for the $β$-decay branching $b_β> 5.9(3)\%$ was determined. The extracted retardation factors for the $γ$ decay of the $10^{(-)}$ state were compared to the available data in neighboring odd-odd thallium isotopes indicating the importance of the $πd_{3/2}$ shell in the isomeric decay and significant structure differences between $^{184}$Tl and $^{186}$Tl.

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arXiv2020

Detailed spectroscopy of doubly magic $^{132}$Sn

The structure of the doubly magic $^{132}_{50}$Sn$_{82}$ has been investigated at the ISOLDE facility at CERN, populated both by the $β^-$decay of $^{132}$In and $β^-$-delayed neutron emission of $^{133}$In. The level scheme of $^{132}$Sn is greatly expanded with the addition of 68 $γ$-transitions and 17 levels observed for the first time in the $β$ decay. The information on the excited structure is completed by new $γ$-transitions and states populated in the $β$-n decay of $^{133}$In. Improved delayed neutron emission probabilities are obtained both for $^{132}$In and $^{133}$In. Level lifetimes are measured via the Advanced Time-Delayed $βγγ$(t) fast-timing method. An interpretation of the level structure is given based on the experimental findings and the particle-hole configurations arising from core excitations both from the \textit{N} = 82 and \textit{Z} = 50 shells, leading to positive and negative parity particle-hole multiplets. The experimental information provides new data to challenge the theoretical description of $^{132}$Sn.

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