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1. Reduction of spectroscopic overlap across the $Z=8$ shell in neutron-rich nuclei

   https://doi.org/10.1103/PhysRevC.109.054325  

   Redpath, T; Guèye, P; Baumann, T; Brown, B A; Cunningham, A; DeYoung, P A; Frank, N; Hoffman, C R; Kuchera, A N; Godoy, B Monteagudo; et al (May 2024, Physical Review C)

   Zhang, Lin (Ed.)

   The recent discovery and spectroscopic measurements of ${}^{27}\mathrm{O}$ and ${}^{28}\mathrm{O}$ suggests the disappearance of the $N=20$ shell structure in these neutron-rich oxygen isotopes. We measured one- and two-proton removal cross sections from ${}^{27}\mathrm{F}$ and ${}^{29}\mathrm{Ne}$ , respectively, extracting spectroscopic factors and comparing them to shell model overlap functions coupled with eikonal reaction model calculations. The invariant mass technique was used to reconstruct the two-body ( ${}^{24}\mathrm{O}+n$ ) and three-body ( ${}^{24}\mathrm{O}+2n$ ) decay energies from knockout reactions of ${}^{27}\mathrm{F}$ (106.2 MeV/u) and ${}^{29}\mathrm{Ne}$ (112.8 MeV/u) beams impinging on a ${}^9\mathrm{Be}$ target. The one-proton removal from ${}^{27}\mathrm{F}$ strongly populated the ground state of ${}^{26}\mathrm{O}$ and the extracted cross section of $3.4_{-1.5}^{+0.3}$ mb agrees with eikonal model calculations that are normalized by the shell model spectroscopic factors and account for the systematic reduction factor observed for single nucleon removal reactions within the models used. For the two-proton removal reaction from ${}^{29}\mathrm{Ne}$ an upper limit of 0.08 mb was extracted for populating states in ${}^{27}\mathrm{O}$ decaying though the ground state of ${}^{26}\mathrm{O}$ . The measured upper limit for the population of the ground state of ${}^{26}\mathrm{O}$ in the two-proton removal reaction from ${}^{29}\mathrm{Ne}$ indicates a significant difference in the underlying nuclear structure of ${}^{27}\mathrm{F}$ and ${}^{29}\mathrm{Ne}$ . Published by the American Physical Society2024 

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2. Properties of Cosmic Lithium Isotopes Measured by the Alpha Magnetic Spectrometer

   https://doi.org/10.1103/PhysRevLett.134.201001  

   Aguilar, M; Ambrosi, G; Anderson, H; Arruda, L; Attig, N; Bagwell, C; Barao, F; Barbanera, M; Barrin, L; Bartoloni, A; et al (May 2025, Physical Review Letters)

   We present the first measurement of cosmic-ray fluxes of ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ isotopes in the rigidity range from 1.9 to 25 GV. The measurements are based on $9.7\times {10}^5$ ${}^6\mathrm{Li}$ and $1.04\times {10}^6$ ${}^7\mathrm{Li}$ nuclei collected by the Alpha Magnetic Spectrometer on the International Space Station from May 2011 to October 2023. We observe that over the entire rigidity range the ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ fluxes exhibit nearly identical time variations and, above $\sim 4\mathrm{GV}$ , the time variations of ${}^6\mathrm{Li}$ , ${}^7\mathrm{Li}$ , He, Be, B, C, N, and O fluxes are identical. Above $\sim 7\mathrm{GV}$ , we find an identical rigidity dependence of the ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ fluxes. This shows that they are both produced by collisions of heavier cosmic-ray nuclei with the interstellar medium and, in particular, excludes the existence of a sizable primary component in the ${}^7\mathrm{Li}$ flux. Published by the American Physical Society2025 

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3. Proton emission in ultraperipheral Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV

   https://doi.org/10.1103/PhysRevC.111.054906  

   Acharya, S; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; et al (May 2025, Physical Review C)

   The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of ${}^{208}\mathrm{Pb}$ nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral ${}^{208}\mathrm{Pb}\text{−}{}^{208}\mathrm{Pb}$ collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ . The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of ${}^{208}\mathrm{Pb}$ . The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes ${}^{206,205,204}\mathrm{Tl}$ . ©2025 CERN, for the ALICE Collaboration2025CERN 

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4. Shedding Light on the Origin of ${}^{204}\mathrm{Pb}$ , the Heaviest $s$ -Process–Only Isotope in the Solar System

   https://doi.org/10.1103/PhysRevLett.133.052702  

   Casanovas-Hoste, A; Domingo-Pardo, C; Lerendegui-Marco, J; Guerrero, C; Tarifeño-Saldivia, A; Krtička, M; Pignatari, M; Calviño, F; Schumann, D; Heinitz, S; et al (July 2024, Physical Review Letters)

   Asymptotic giant branch stars are responsible for the production of most of the heavy isotopes beyond Sr observed in the solar system. Among them, isotopes shielded from the $r$ -process contribution by their stable isobars are defined as $s$ -only nuclei. For a long time the abundance of ${}^{204}\mathrm{Pb}$ , the heaviest $s$ -only isotope, has been a topic of debate because state-of-the-art stellar models appeared to systematically underestimate its solar abundance. Besides the impact of uncertainties from stellar models and galactic chemical evolution simulations, this discrepancy was further obscured by rather divergent theoretical estimates for the neutron capture cross section of its radioactive precursor in the neutron-capture flow, ${}^{204}\mathrm{Tl}$ ( $t_{1/2}=3.78\mathrm{yr}$ ), and by the lack of experimental data on this reaction. We present the first ever neutron capture measurement on ${}^{204}\mathrm{Tl}$ , conducted at the CERN neutron time-of-flight facility n_TOF, employing a sample of only 9 mg of ${}^{204}\mathrm{Tl}$ produced at the Institute Laue Langevin high flux reactor. By complementing our new results with semiempirical calculations we obtained, at the $s$ -process temperatures of $kT\approx 8\mathrm{keV}$ and $kT\approx 30\mathrm{keV}$ , Maxwellian-averaged cross sections (MACS) of 580(168) mb and 260(90) mb, respectively. These figures are about 3% lower and 20% higher than the corresponding values widely used in astrophysical calculations, which were based only on theoretical calculations. By using the new ${}^{204}\mathrm{Tl}$ MACS, the uncertainty arising from the ${}^{204}\mathrm{Tl}(\mathrm{n},\gamma )$ cross section on the $s$ -process abundance of ${}^{204}\mathrm{Pb}$ has been reduced from $\sim 30\%$ down to $+8\%/-6\%$ , and the $s$ -process calculations are in agreement with the latest solar system abundance of ${}^{204}\mathrm{Pb}$ reported by K. Lodders in 2021. Published by the American Physical Society2024 

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5. Precision measurement of lifetime and branching ratios of the $4f^{13}5d6s^1{[5/2]}_{5/2}$ state in ${\mathrm{Yb}}^{+}$ ions

   https://doi.org/10.1103/mwwc-kng1  

   Duraisamy_Suganthi, Midhuna; So, Visal; Menon, Abhishek; Tomaras, George; Zhuravel, Roman; Pagano, Guido (December 2025, Physical Review Research)

   We report spectroscopic and time-resolved experimental observations to characterize the $\left[\mathrm{Xe}\right]4f^{13}\left({}^{2}F_{5/2}^o\right)5d6s\left({}^{1}D\right){}^1{[5/2]}_{5/2}^o$ state in ${}^{172}\mathrm{Yb}^{+}$  ions. We access this state from the metastable $4f^{14}5d\left({}^{2}D_{3/2,5/2}\right)$ manifold and observe an unexpectedly long lifetime of $\tau =37.9\left(9\right)\mu \mathrm{s}$  that allows visible Rabi oscillations and resolved-sideband spectroscopy. Using a combination of coherent population dynamics, high-fidelity detection and heralded state preparation, and optical pumping methods, we measure the branching ratios to the ${}^{2}D_{3/2}, {}^{2}D_{5/2}$ , and ${}^{2}S_{1/2}$ states to be $0.359\left(2\right)$ , 0.639(2), and $0.0023\left(16\right)$ , respectively. The branching ratio to the $4f^{13}6s^2\left({{}^{2}F}_{7/2}\right)$ is compatible with zero within our experimental resolution. We also report measurements of Landé $g$ -factor of the ${}^1{[5/2]}_{5/2}^o$ state. Further, the branching ratio of the ${}^{2}D_{5/2}$ to ${}^{2}S_{1/2}$ decay in ${}^{172}\mathrm{Yb}^{+}$  was measured to be 0.188(3), improving its relative uncertainty by an order of magnitude. Our measurements provide experimental benchmarks for better understanding the atomic structure of ${\mathrm{Yb}}^{+}$  ions, which still lacks accurate numerical descriptions, and the use of high-lying excited states for partial detection and qubit manipulation in the architecture. 

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