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1. Lifetimes of excited states in $$^{16}$$C as a benchmark for ab initio developments

   https://doi.org/10.1140/epja/s10050-024-01396-2  

   Mathy, M; Petri, M; Roth, R; Wagner, L; Heil, S; Ayangeakaa, A D; Bottoni, S; Carpenter, M P; Crawford, H L; Fallon, P; et al (September 2024, The European Physical Journal A)

   Abstract Lifetimes of higher-lying states ($$2_2^+$$ $2_2^{+}$and$$4_1^+$$ $4_1^{+}$) in$$^{16}$$ $_{}^{16}$C have been measured, employing the Gammasphere and Microball detector arrays, as key observables to test and refine ab initio calculations based on interactions developed within chiral Effective Field Theory. The presented experimental constraints to these lifetimes of$$\tau ({2_2^+}) = [\,244, 446]\,~\textrm{fs}$$ $\tau \left(2_2^{+}\right)=[244,446]\text{fs}$and$$\tau ({4_1^+}) = [\,1.8, 4]\,~\textrm{ps}$$ $\tau \left(4_1^{+}\right)=[1.8,4]\text{ps}$, combined with previous results on the lifetime of the$$2_1^+$$ $2_1^{+}$state of$$^{16}$$ $_{}^{16}$C, provide a rather complete set of key observables to benchmark the theoretical developments. We present No-Core Shell-Model calculations using state-of-the-art chiral 2- (NN) and 3-nucleon (3N) interactions at next-to-next-to-next-to-leading order for both the NN and the 3N contributions and a generalized natural-orbital basis (instead of the conventional harmonic-oscillator single-particle basis) which reproduce, for the first time, the experimental findings remarkably well. The level of agreement of the new calculations as compared to the CD-Bonn meson-exchange NN interaction is notable and presents a critical benchmark for theory. 

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2. Formation of Oxygen Vacancies in Cr3+-Doped Hydroxyapatite Nanofibers and Their Role in Generating Paramagnetism

   https://doi.org/10.1007/s44174-024-00191-3  

   Carrera, Karime; Huerta, Verónica; Orozco, Victor; Matutes, José; Urbieta, Ana; Fernández, Paloma; Martínez, Fabián; Graeve, Olivia_A; Herrera, Manuel (May 2024, Biomedical Materials & Devices)

   Abstract We demonstrate that doping hydroxyapatite (HAp) with Cr³⁺ions induces oxygen vacancies, contributing to paramagnetism. Cathodoluminescence and photoluminescence analyses reveal increased oxygen vacancy formation in$${\text{O}}{\text{H}}^{-}$$ ${\text{OH}}^{-}$and$${\text{P}}{\text{O}}_{4}^{3-}$$ ${\text{PO}}_4^{3-}$groups with rising Cr³⁺concentrations, highlighted by stronger cathodoluminescence emissions at 2.57 and 2.95 eV and the photoluminescence emission at 3.32 eV. Raman spectroscopy shows new modes at 900 and 970 cm⁻¹, indicating distortion of thev₁vibrational mode due to Cr³⁺substitution at Ca(II) sites of the HAp lattice. X-ray photoelectron spectroscopy confirms Cr³⁺in the HAp:Cr. Magnetometry reveals a shift from diamagnetism in pure HAp to increasing paramagnetism in HAp:Cr with higher Cr³⁺content, achieving 0.0460 emu/g at 10 kOe with concentrations higher than 2.9 at.%. This paramagnetism is attributed to Cr³⁺ions and singly ionized oxygen vacancies$$V^{\prime}_{{\text{O}}}$$ $V_{\text{O}}^{\prime }$aligning along an external magnetic field, with$$V^{\prime}_{{\text{O}}}$$ $V_{\text{O}}^{\prime }$formation linked to$${\text{PO}}_{4}^{{3}-}$$ ${\text{PO}}_4^{3-}$replacement by$${\text{PO}}_{3}^{{2}-}$$ ${\text{PO}}_3^{2-}$in HAp. 

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3. Photo-response of the $$N=Z$$ nucleus $$^{24}$$Mg

   https://doi.org/10.1140/epja/s10050-023-01111-7  

   Deary, J; Scheck, M; Schwengner, R; O’Donnell, D; Bemmerer, D; Beyer, R; Hensel, Th; Junghans, A R; Kögler, T; Müller, S E; et al (September 2023, The European Physical Journal A)

   Abstract The electricE1 and magneticM1 dipole responses of the$$N=Z$$ $N=Z$nucleus$$^{24}$$ ${}^{24}$Mg were investigated in an inelastic photon scattering experiment. The 13.0 MeV electrons, which were used to produce the unpolarised bremsstrahlung in the entrance channel of the$$^{24}$$ ${}^{24}$Mg($$\gamma ,\gamma ^{\prime }$$ $\gamma ,{\gamma }^{\prime }$) reaction, were delivered by the ELBE accelerator of the Helmholtz-Zentrum Dresden-Rossendorf. The collimated bremsstrahlung photons excited one$$J^{\pi }=1^-$$ $J^{\pi }=1^{-}$, four$$J^{\pi }=1^+$$ $J^{\pi }=1^{+}$, and six$$J^{\pi }=2^+$$ $J^{\pi }=2^{+}$states in$$^{24}$$ ${}^{24}$Mg. De-excitation$$\gamma $$ $\gamma$rays were detected using the four high-purity germanium detectors of the$$\gamma $$ $\gamma$ELBE setup, which is dedicated to nuclear resonance fluorescence experiments. In the energy region up to 13.0 MeV a total$$B(M1)\uparrow = 2.7(3)~\mu _N^2$$ $B\left(M1\right)\uparrow =2.7\left(3\right){\mu }_N^2$is observed, but this$$N=Z$$ $N=Z$nucleus exhibits only marginalE1 strength of less than$$\sum B(E1)\uparrow \le 0.61 \times 10^{-3}$$ $\sum B\left(E1\right)\uparrow \le 0.61\times {10}^{-3}$ e$$^2 \, $$ ${}^2$fm$$^2$$ ${}^2$. The$$B(\varPi 1, 1^{\pi }_i \rightarrow 2^+_1)/B(\varPi 1, 1^{\pi }_i \rightarrow 0^+_{gs})$$ $B(\Pi 1,1_i^{\pi }\to 2_1^{+})/B(\Pi 1,1_i^{\pi }\to 0_{\mathrm{gs}}^{+})$branching ratios in combination with the expected results from the Alaga rules demonstrate thatKis a good approximative quantum number for$$^{24}$$ ${}^{24}$Mg. The use of the known$$\rho ^2(E0, 0^+_2 \rightarrow 0^+_{gs})$$ ${\rho }^2(E0,0_2^{+}\to 0_{\mathrm{gs}}^{+})$strength and the measured$$B(M1, 1^+ \rightarrow 0^+_2)/B(M1, 1^+ \rightarrow 0^+_{gs})$$ $B(M1,1^{+}\to 0_2^{+})/B(M1,1^{+}\to 0_{\mathrm{gs}}^{+})$branching ratio of the 10.712 MeV$$1^+$$ $1^{+}$level allows, in a two-state mixing model, an extraction of the difference$$\varDelta \beta _2^2$$ $\Delta {\beta }_2^2$between the prolate ground-state structure and shape-coexisting superdeformed structure built upon the 6432-keV$$0^+_2$$ $0_2^{+}$level. 

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4. Spherical convex hull of random points on a wedge

   https://doi.org/10.1007/s00208-023-02704-9  

   Besau, Florian; Gusakova, Anna; Reitzner, Matthias; Schütt, Carsten; Thäle, Christoph; Werner, Elisabeth_M (August 2023, Mathematische Annalen)

   Abstract Consider two half-spaces$$H_1^+$$ $H_1^{+}$and$$H_2^+$$ $H_2^{+}$in$${\mathbb {R}}^{d+1}$$ $R^{d+1}$whose bounding hyperplanes$$H_1$$ $H_1$and$$H_2$$ $H_2$are orthogonal and pass through the origin. The intersection$${\mathbb {S}}_{2,+}^d:={\mathbb {S}}^d\cap H_1^+\cap H_2^+$$ $S_{2,+}^d:=S^d\cap H_1^{+}\cap H_2^{+}$is a spherical convex subset of thed-dimensional unit sphere$${\mathbb {S}}^d$$ $S^d$, which contains a great subsphere of dimension$$d-2$$ $d-2$and is called a spherical wedge. Choosenindependent random points uniformly at random on$${\mathbb {S}}_{2,+}^d$$ $S_{2,+}^d$and consider the expected facet number of the spherical convex hull of these points. It is shown that, up to terms of lower order, this expectation grows like a constant multiple of$$\log n$$ $logn$. A similar behaviour is obtained for the expected facet number of a homogeneous Poisson point process on$${\mathbb {S}}_{2,+}^d$$ $S_{2,+}^d$. The result is compared to the corresponding behaviour of classical Euclidean random polytopes and of spherical random polytopes on a half-sphere. 

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5. Modular apparatus for nuclear reactions spectroscopy (MARS): characterization and first application to determine $$^{12}$$C($$^6$$Li,$$^4$$He)$$^{14}\hbox {N}^{g.s}$$ nuclear reaction cross sections

   https://doi.org/10.1140/epjp/s13360-025-06305-0  

   Garrido-Gómez, L; Vegas-Díaz, A; Alvarez, M_A G; Fernández-García, J P; Fernández, B; Ferrer, F J; Lopez-Aires, D (May 2025, The European Physical Journal Plus)

   Abstract This work presents MARS (Modular apparatus for nuclear reactions spectroscopy) and its characterization prior to its first application to measure$$^6$$ $_{}^6$Li+$$^{12}$$ $_{}^{12}$C nuclear reactions. Measurements were performed at the 3 MV tandem accelerator of the CNA (National Accelerator Center), in Seville, Spain. The$$^{6}$$ $_{}^6$Li projectiles were accelerated at energies around the$$^6$$ $_{}^6$Li+$$^{12}$$ $_{}^{12}$C Coulomb barrier ($$V^{\text {cm}}_{B}\sim 3.0$$ $V_B^{\text{cm}}\sim 3.0$MeV - center of mass and$$V^{\text {lab}}_{B}\sim 4.5$$ $V_B^{\text{lab}}\sim 4.5$MeV - laboratory frame). Using a$$^{6}\hbox {Li}^{2+}$$ $_{}^6{\text{Li}}^{2+}$beam, we measured at 13 laboratory energies from 4.00 to 7.75 MeV. Thus, we present the excitation function of$$^{12}$$ $_{}^{12}$C($$^6$$ $_{}^6$Li,$$^4$$ $_{}^4$He)$$^{14}\hbox {N}^{g.s.}$$ $_{}^{14}{\text{N}}^{g.s.}$reaction, at 2 backward angles ($$110.0^\circ $$ $110.0^{\circ }$and$$140.0^\circ $$ $140.0^{\circ }$). The projectile dissociation, leading to this reaction, increases with the bombarding energies around the Coulomb barrier. This dissociation is favored at an optimum energy$$E_{b}^{\text {op}}$$ $E_b^{\text{op}}$$$\ge $$ $\ge$$$V_{B}$$ $V_B$+$$|Q_{bu}|$$ $|Q_{\mathrm{bu}}|$, where$$V_{B}$$ $V_B$is the Coulomb barrier of the system, and$$|Q_{bu}|$$ $|Q_{\mathrm{bu}}|$is the module ofQ-value for the$$^6$$ $_{}^6$Li dissociation into$$^4$$ $_{}^4$He+$$^2$$ $_{}^2$H. This result corroborates a systematic analysis of weakly bound projectiles reacting on several targets [1]. 

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