Fri·Feb 7, 2020Friday·February 7, 2020

1. 01*

   Evolution of the N=20 and 28 Shell Gaps and 2-particle-2-hole states in the FSU Interaction

   R. S. Lubna · K. Kravvaris · S. L. Tabor. Vandana Tripathi · E. Rubino · A. Volya

   The FSU $spsdfp$ cross-shell interaction for the shell model was successfully fitted to a wide range of mostly intruder negative parity states of the $sd$ shell nuclei. This paper reports the application of the FSU interaction to systematically trace out the relative positions of the effective single-particle energies of the $0f_{7/2}$ and $1p_{3/2}$ orbitals, the evolution from normally ordered low-lying states to the "Island of Inversion" (IoI), and the behavior of a wide range of excited states with a $0f_{7/2}$ proton and neutron coupled to maximum spin of $7\hslash$. Above a proton number of about 13 the $0f_{7/2}$ orbital lies below that of $1p_{3/2}$, which is considered normal ordering, but systematically at $Z=10$ to $12$ the orbitals cross. The calculations reproduce well the 2p2h - 0p0h inversion in the configurations of nuclei inside the IoI, they reproduce the absolute binding energies and the transition to normal ordering as the proton number approaches that of the neutrons. The important role of $1p_{3/2}$ neutron pairs in the IoI is also demonstrated. The calculations account well for the energies of the fully aligned states with 0, 1, or 2 individual $sd$ nucleon aligned in spin with the aligned $\pi 0f_{7/2}$ - $\nu 0f_{7/2}$ pair and reproduce well their systematic variation with $A$ and number of aligned $sd$ nucleons. The results presented in this paper give hope for the predictive power of the FSU interaction for more exotic nuclei to be explored in near future.

   nucl-exnucl-thPRResearch(2020)·51 citations
2. 02*

   Measurement of the ${}^{154}$Gd(n,$\gamma$) cross section and its astrophysical implications

   A. Mazzone · S. Cristallo · C. Massimi · the n_TOF Collaboration

   The neutron capture cross section of ${}^{154}$Gd was measured from 1 eV to 300 keV in the experimental area located 185 m from the CERN n\_TOF neutron spallation source, using a metallic sample of gadolinium, enriched to 67$\%$ in ${}^{154}$Gd. The capture measurement, performed with four C${}_6$D${}_6$ scintillation detectors, has been complemented by a transmission measurement performed at the GELINA time-of-flight facility (JRC-Geel), thus minimising the uncertainty related to sample composition. An accurate Maxwellian averaged capture cross section (MACS) was deduced over the temperature range of interest for s process nucleosynthesis modeling. We report a value of 880(50) mb for the MACS at $kT=30$ keV, significantly lower compared to values available in literature. The new adopted ${}^{154}$Gd(n,$\gamma$) cross section reduces the discrepancy between observed and calculated solar s-only isotopic abundances predicted by s-process nucleosynthesis models.

   nucl-exPLB(2020)·12 citations
3. 03*

   Ab initio computation of charge densities for Sn and Xe isotopes

   P. Arthuis🇬🇧 · C. Barbieri🇬🇧 · M. Vorabbi🇺🇸 · P. Finelli🇮🇹

   We present the first ab initio calculations for open-shell nuclei past the tin isotopic line, focusing on Xe isotopes as well as doubly-magic Sn isotopes. We show that, even for moderately hard interactions, it is possible to obtain meaningful predictions and that the NNLOsat chiral interaction predicts radii and charge density distributions close to the experiment. We then make a new prediction for ${}^{100}$Sn. This paves the way for ab initio studies of exotic charge density distributions at the limit of the present ab initio mass domain, where experimental data is becoming available. The present study closes the gap between the largest isotopes reachable by ab initio methods and the smallest exotic nuclei accessible to electron scattering experiments.

   ↳ nucl-thnucl-exPRL(2020)·68 citations
4. 04*

   Solar Flare Detection Method using Rn-222 Radioactive Source

   Jonathan Walg · Anatoly Rodnianski · Itzhak Orion

   Solar neutrino detection is known to be a very challenging task, due to the minuscule absorption cross-section and mass of the neutrino. One research showed that relative large solar-flares affected the decay-rates of Mn-54 in December 2006. Since most the radiation emitted during a solar flare are blocked before reaching the earth surface, it should be assumed that such decay-rate changes could be due to neutrino flux increase from the sun, in which only neutrinos can penetrate the radionuclide. This study employs the Rn-222 radioactive source for the task of solar flare detection, based on the prediction that it will provide a stable gamma ray counting rate. In order to ascertain counting stability, three counting systems were constructed to track the count-rate changes. The Rn-222 count-rate measurements showed several radiation counting dips, indicating that the radioactive nuclide can be affected by order of magnitude neutrino flux change from the sun. We conclude that using the cooled Radon source obtained the clearest responses, and therefore this is the preferable system for detecting neutrino emissions from a controlled source.

   ↳ astro-ph.SRnucl-exphysics.ins-det0 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.