Investigation of the ground-state spin inversion in the neutron-rich 47,49Cl isotopes

A first γ -ray study of 47,49Cl spectroscopy was performed at the Radioactive Isotope Beam Factory with 50Ar projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS device. Prompt deexcitation γ rays were measured with the NaI(Tl) array DALI2+. Through the one-proton knockout reaction 50Ar(p, 2p), a spin assignment could be determined for the low-lying states of 49Cl from the momentum distribution obtained with the SAMURAI spectrometer. A spin-parity Jπ = 3/2+ is deduced for the ground state of 49Cl, similar to the recently studied N = 32 isotope 51K. The evolution of the energy difference E(1/2+ 1 ) − E(3/2+ 1 ) is compared to state-of-the-art theoretical predictions.Ministerio de Ciencia de España, Innovación y Universidades y fondos FEDER. FIS2017-88410-PFondo Nacional de Investigación, Desarrollo e Innovación de Hungría. Proyecto No. K128947.The Office of Nuclear Physics, U.S. Department of Energy. De-sc0018223The United Kingdom Science and Technology Facilities Council (STFC). ST/L005816/1Natural Sciences and Engineering Research Council of Canada (NSERC). SAPIN-2016-00033, SAPIN-2018- 00027 y RGPAS-2018-522453

A squalene-hopene cyclase in Schizosaccharomyces japonicus represents a eukaryotic adaptation to sterol-limited anaerobic environments

Biosynthesis of sterols, which are key constituents of canonical eukaryotic membranes, requires molecular oxygen. Anaerobic protists and deep-branching anaerobic fungi are the only eukaryotes in which a mechanism for sterol-independent growth has been elucidated. In these organisms, tetrahymanol, formed through oxygen-independent cyclization of squalene by a squalene-tetrahymanol cyclase, acts as a sterol surrogate. This study confirms an early report [C. J. E. A. Bulder, Antonie Van Leeuwenhoek, 37, 353-358 (1971)] that Schizosaccharomyces japonicus is exceptional among yeasts in growing anaerobically on synthetic media lacking sterols and unsaturated fatty acids. Mass spectrometry of lipid fractions of anaerobically grown Sch. japonicus showed the presence of hopanoids, a class of cyclic triterpenoids not previously detected in yeasts, including hop-22(29)-ene, hop17(21)-ene, hop-21(22)-ene, and hopan-22-ol. A putative gene in Sch. japonicus showed high similarity to bacterial squalene-hopene cyclase (SHC) genes and in particular to those of Acetobacter species. No orthologs of the putative Sch. japonicus SHC were found in other yeast species. Expression of the Sch. japonicus SHC gene (Sjshc1) in Saccharomyces cerevisiae enabled hopanoid synthesis and stimulated anaerobic growth in sterol-free media, thus indicating that one or more of the hopanoids produced by SjShc1 could at least partially replace sterols. Use of hopanoids as sterol surrogates represents a previously unknown adaptation of eukaryotic cells to anaerobic growth. The fast anaerobic growth of Sch. japonicus in sterol-free media is an interesting trait for developing robust fungal cell factories for application in anaerobic industrial processes.Proteomic

Core-coupled states and split proton-neutron quasi-particle multiplets in 122-126Ag

Neutron-rich silver isotopes were populated in the fragmentation of a 136Xe beam and the relativistic fission of 238U. The fragments were mass analyzed with the GSI Fragment separator and subsequently implanted into a passive stopper. Isomeric transitions were detected by 105 HPGe detectors. Eight isomeric states were observed in 122-126Ag nuclei. The level schemes of 122,123,125Ag were revised and extended with isomeric transitions being observed for the first time. The excited states in the odd-mass silver isotopes are interpreted as core-coupled states. The isomeric states in the even-mass silver isotopes are discussed in the framework of the proton-neutron split multiplets. The results of shell-model calculations, performed for the most neutron-rich silver nuclei are compared to the experimental data

Structural evolution in the neutron-rich nuclei 106Zr and 108Zr

The low-lying states in 106Zr and 108Zr have been investigated by means of {\beta}-{\gamma} and isomer spectroscopy at the RI beam factory, respectively. A new isomer with a half-life of 620\pm150 ns has been identified in 108Zr. For the sequence of even-even Zr isotopes, the excitation energies of the first 2+ states reach a minimum at N = 64 and gradually increase as the neutron number increases up to N = 68, suggesting a deformed sub-shell closure at N = 64. The deformed ground state of 108Zr indicates that a spherical sub-shell gap predicted at N = 70 is not large enough to change the ground state of 108Zr to the spherical shape. The possibility of a tetrahedral shape isomer in 108Zr is also discussed.Comment: 10 pages, 3 figures, Accepted for publication in Phys. Rev. Let

Intermediate-energy Coulomb excitation of 104 Sn: Moderate E2 strength decrease approaching 100 Sn

International audienceThe reduced transition probability B(E2)↑ of the first excited 2 + state in the nucleus 104 Sn was measured via Coulomb excitation in inverse kinematics at intermediate energies. A value of 0.173(28) e 2 b 2 was extracted from the absolute cross section on a Pb target. Feeding contributions in 104 Sn from higher lying states were estimated by a reference measurement of the stable 112 Sn. Corresponding only to a moderate decrease of excitation strength relative to the almost constant values observed in the proton-rich, even-A 106−114 Sn isotopes, present state-of-the-art shell-model predictions, which include proton and neutron excitations across the N = Z = 50 shell closures as well as standard polarization charges, underestimate the experimental findings