Shape staggering of midshell mercury isotopes from in-source laser spectroscopy compared with density-functional-theory and Monte Carlo shell-model calculations

Neutron-deficient 177−185Hg isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility in an experiment combining different detection methods tailored to the studied isotopes. These include either α-decay tagging or multireflection time-of-flight gating for isotope identification. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring for the first time the isotope shifts and hyperfine structures of 177−180Hg. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole, and electric quadrupole moments of the odd-A isotopes and arguments in favor of I=7/2 spin assignment for 177,179Hg were deduced. Experimental results are compared with density functional theory (DFT) and Monte Carlo shell model (MCSM) calculations. DFT calculations using Skyrme parametrizations predict a jump in the charge radius around the neutron N=104 midshell, with an odd-even staggering pattern related to the coexistence of nearly degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiments out of reach for current functionals. Despite this inherent difficulty, the SLy5s1 and a modified UNEDF1SO parametrization predict a qualitatively correct staggering that is off by two neutron numbers. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: a substantial change in occupancy of the proton πh9/2 and neutron νi13/2 orbitals

Algorithm development of structural variables for slope reinforcement of hydrotechnic structures with synthetic materials

The construction of hydrotechnic structures out of watercourse area is usually done with grass seeding above a vegetative soil layer. For stability of slope protection, during and after construction, it is suggested that vegetated soil is reinforced with cubic geosynthetic mats. To choose a geosynthetic material the algorithm is offered, taking into account conditions that provide resistance of vegetated soil layer, and depending on forces that act upon the slope and considering changes of material properties in course of time technological peculiarities of its placement

Corrosion Behavior of Candidate Functional Materials for Molten Salts Reactors in LiF–NaF–KF Containing Actinide Fluoride Imitators

Molten fluorides of alkali metals are considered a technological medium for molten salt reactors (MSRs). However, these media are known to be extremely corrosive. The successful implementation of high-temperature technological devices using molten alkali metal fluorides requires the selection of such structural materials that have high corrosion resistance in melts with compositional characteristic of MSRs. In this research, the corrosion behavior of 12Cr18Ni10Ti steel, the alloy Ni60Cr20Mo15, and the alloy Monel 404 (Ni50Cu50) was investigated in the LiF–NaF–KF eutectic melt, containing additions of CeF3 and NdF3 from 0 to 5 wt.% as imitator fluorides of actinides in an inert argon atmosphere at 550 °C for 100 h. Gravimetry, energy-dispersive X-ray (EDX) microanalysis of surfaces and cross-section of samples, and ICP-MS were used to establish the corrosion behavior of the investigated alloys. Corrosion resistance of the studied materials was found to decrease in a row from Monel 404 > Hastelloy C2000 > 12Cr18Ni10Ti. The addition of cerium fluoride into the melt resulted in the additional etching of the alloy surface. The addition of neodymium fluoride resulted in the formation of the point/inter-crystalline corrosion damages in the sample bulk. The samples of steel 12Cr18Ni10Ti were subjected to local cracking corrosion. The austenitic nickel-based alloys suffered specific local corrosion with formation of subsurface voids. Excellent corrosion resistance of the Monel alloy under the test conditions was found

In-source laser photoionization spectroscopy of Bi isotopes:accuracy of the technique and methods of data analysis

The in-source laser photoionization spectroscopy was applied to study neutron-deficient Bi isotopes. Data analysis and accuracy-related aspects of this technique are discussed. The accuracy of the peak position evaluation is estimated. An “integration method” for nuclear spin determination in the case of partially resolved hyperfine spectra is discussed in detail.</p

In-source laser photoionization spectroscopy of Bi isotopes: accuracy of the technique and methods of data analysis

The in-source laser photoionization spectroscopy was applied to study neutron-deficient Bi isotopes. Data analysis and accuracy-related aspects of this technique are discussed. The accuracy of the peak position evaluation is estimated. An “integration method” for nuclear spin determination in the case of partially resolved hyperfine spectra is discussed in detail

In-source laser spectroscopy of 75,77,78Cu: Direct evidence for a change in the quasiparticle energy sequence in 75,77Cu and an absence of longer-lived isomers in 78Cu

This paper describes measurements on the isotopes 75,77,78Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the context of this and other, higher resolution, methods applied to copper isotopes in the range 57−78Cu. The data, analyzed in comparison with previous results on the lighter isotopes 59,63Cu, establish the ground-state nuclear spin of 75,77Cu as 5/2 and yield their magnetic dipole moments as +1.01(5)μN and +1.61(5)μN, respectively. The results on 78Cu show no evidence for long-lived isomerism at this mass number and are consistent with a spin in the range 3–6 and moment of 0.0(4) μN.status: publishe

Resonant laser ionization of polonium at rilis-isolde for the study of ground- and isomer-state properties

Three new ionization schemes for polonium have been tested with the resonant ionization laser ion source (rilis) during the on-line production of 196Po in a UCx target at isolde. The saturation of the atomic transitions has been observed and the yields of the isotope chain 193–198,200,202,204Po have been measured. This development provides the necessary groundwork for performing in-source resonant ionization spectroscopy on the neutron-deficient polonium isotopes (Z = 8

Resonant laser ionization of polonium at RILIS-ISOLDE for the study of ground- and isomer-state properties

Three new ionization schemes for polonium have been tested with the resonant ionization laser ion source (RILIS) during the on-line production of 196Po in a UCx target at ISOLDE. The saturation of the atomic transitions has been observed and the yields of the isotope chain 193–198,200,202,204Po have been measured. This development provides the necessary groundwork for performing in-source resonant ionization spectroscopy on the neutron-deficient polonium isotopes (Z = 84).status: publishe

Gamow-Teller decay population of 64Ni levels in the decay of 1+ 64Co

The 64Co β-decay feeding levels in the well-studied 64Ni nucleus were investigated. Whereas the previously known 64Co decay scheme merely contained 2 γ rays, the decay scheme established in this work contains 18, of which 5 are observed in this work and 6 were previously observed in an (n,γ) study but not placed in the 64Ni level scheme. Surprisingly, one additional level—placed at an excitation energy of 3578.7 keV—could be determined. The observed β-decay paths involve allowed νf5/2 → πf7/2 and νp1/2 → πp3/2 transitions. Three strongly fed levels around 4 MeV are interpreted to possess possible proton-intruder characterstatus: publishe