International audienceThe occurrence of the bubble-like structure has been studied, in the light of pseudospin degeneracy, within the relativistic Hartree-Fock-Bogoliubov (RHFB) theory. It is concluded that the charge/neutron bubble-like structure is predicted to occur in the mirror system of {Si34,Ca34} commonly by the selected Lagrangians, due to the persistence of Z(N)=14 subshell gaps above which the π(ν)2s1/2 states are not occupied. However, for the popular candidate Ar46, the RHFB Lagrangian PKA1 does not support the occurrence of the bubble-like structure in the charge (proton) density profiles, due to the almost degenerate pseudospin doublet {π2s1/2,π1d3/2} and coherent pairing effects. The formation of a semibubble in heavy nuclei is less possible as a result of small pseudospin-orbit (PSO) splitting, while it tends to appear at Z=120 superheavy systems which coincides with large PSO splitting of the doublet {π3p3/2,π2f5/2} and couples with significant shell effects. Pairing correlations, which can work against bubble formation, significantly affect the PSO splitting. Furthermore, we found that the influence on semibubble formation due to different types of pairing interactions is negligible. The quenching of the spin-orbit splitting in the p orbit has been also stressed, and it may be considered the hallmark for semibubble nuclei

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The occurrence of the proton bubble-like structure has been studied within the relativistic Hartree-Fock-Bogoliubov (RHFB) and relativistic Hartree-Bogoliubov (RHB) theories by exploring the bulk properties, the charge density profiles and single proton spectra of argon isotopes and N = 28 isotones. It is found that the RHFB calculations with PKA1 effective interaction, which can properly reproduce the charge radii of argon isotopes and the Z = 16 proton shell nearby, do not support the occurrence of the proton bubble-like structure in argon isotopes due to the prediction of deeper bound proton orbit π2s 1/2 than π1d 3/2 . For N = 28 isotones, 42 Si and 40 Mg are predicted by both RHFB and RHB models to have the proton bubble-like structure, owing to the large gap between the proton π2s 1/2 and π1d 5/2 orbits, namely the Z = 14 proton shell. Therefore, 42 Si is proposed as the potential candidate of proton bubble nucleus, which has longer life-time than 40 Mg.

Oxygen vacancy distribution has a direct effect on the crystal structure and physical properties of complex oxides, resulting in versatile applications. Here, we report on a reversible topotactic phase transition between the perovskite and brownmillerite structures for the LaCoO3−δ (δ  =  0–0.5) epitaxial film by annealing the sample under different conditions. In the atmosphere of 2  ×  10−4 Pa, LaCoO3 film is transformed from the perovskite structure to the brownmillerite structure when annealing temperature exceeds 500 °C. Meanwhile, the magnetic order transits from ferromagnetic to anti-ferromagnetic. Variable-range hopping demonstrates the electronic transport process for both phases. The incorporation of oxygen vacancies results in an upward shift of the lnρ-T−1/4 curve, without affecting the lnρ-T−1/4 slope. We found signatures for preferential distribution for oxygen vacancies; the latter prefer to appear near high spin Co3+ ions in the initial stage when they are introduced into the lattice, resulting in abnormal magnetic and transport behaviors.

The simultaneous desulfurization of 2-mercapto-5-methyl-1,3,4-thiadiazole with CuCl(2) x 2H(2)O via mutual diffusion in solvents results in the isolation of air-stable dark-green crystals of [Cu(H(4)C(3)N(2)S)Cl(2)](n) (approximately 65% yield). The structure is characterized by a unique one-dimensional copper chain bridged by diazine N-N single bonds rather than halogens, in sharp contrast with the halide bridging mode in conventional copper halide coordination polymers. Each Cu(II) ion shows a square planar coordination geometry featuring a strong Jahn-Teller distortion, as also supported by EPR data. The phase follows a Curie-Weiss paramagnetic behavior over 6-300 K. However, the intrachain antiferromagnetic interaction is evident (-2J = 21.1 cm(-1)). Such magnetic coupling is related to the interplay between the Cu(II)-d(x2-y2) and diazine N-N p-orbitals.

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Half-life of proton radioactivity of spherical proton emitters is studied within the scheme of covariant density functional (CDF) theory, and for the first time the potential barrier that prevents the emitted proton is extracted with the similarity renormalization group (SRG) method, in which the spin-orbit potential along with the others that turn out to be non-negligible can be derived automatically. The spectroscopic factor that is significant is also extracted from the CDF calculations. The estimated half-lives are found in good agreement with the experimental values, which not only confirms the validity of the CDF theory in describing the proton-rich nuclei, but also indicates the prediction power of present approach to calculate the half-lives and in turn to extract the structural information of proton emitters. With continuous development of the radioactive ion beam facilities, the exotic nuclei far away from the β-stability line attract extensive interests for the new phenomena they present. One of the typical representatives is the proton radioactivity at the vicinity of proton drip line, firstly observed in an isomeric state of 53 Co in 1970 [1, 2]. Since then more and more proton emitters ranging from Z = 51 to 83 have been identified with nuclear ground states or isomeric states [3]. Essentially, it is significant to study the proton emission which corresponds to the fundamental existence limits of neutron-deficient nuclei, i.e., the proton drip line, and it also can be treated as the inverse reaction of the rapid proton capture process that plays an important role in understanding the origin of the elements in the universe [4]. Moreover specific aspects of nucleonic interactions could be isolated and amplified in the proton emitters due to their extreme proton excess [5]. In particular combined with theoretical analysis, nuclear structural information can be extracted from measurements of half-life, proton branching ratio (fine structure), the energy and angular momentum transfer l carried away by the emitted proton, etc. The fact that the half-life of proton emission is sensitive to the Q-value and angular momentum transfer l, not only helps to determine the orbit of the emitted proton in parent nucleus in experiments, but also provides an efficient way to test theoretical models in exploring the neutron-deficient nuclear systems.Theoretically various methods have been employed in describing the properties of proton emitters, such as the spectroscopic factor and the half-life (for review see Ref.[6]). For the half-life that can be measured experimentally, a semiclassical method is applied by treating the proton emission as quantum tunneling through a potential barrier, which is composed of the Coulomb repulsion, centrifugal barrier and effective nuclear potential. Several approaches have been employed in constructing the effective nuclear potential, e.g., in terms of the density-dependent M3Y effective interaction [7], the effective interaction of Jeukenne, Lejeume, and Mahaux [8], the renormalized...