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[en] The hyperfine structures and isotope shifts of Potassium from N = 19 to N = 32 (38,39,42,44,46,47-51K) have been measured successfully. From these spins, magnetic moments and changes in root mean square charge radii δ left angle r2 right angle have been extracted. The model independent spin determinations obtained in this work clarify the level schemes of neutron rich Potassium isotopes. For the first time the range and extend of the π d3/2 to π s1/2 ground state inversion has been established. The extracted δ left angle r2 right angle, in conjunction with those of Ca, Cr, Mn and Fe provide a first insight into the regional Z dependence of the evolution of nuclear size beyond N = 28.
[en] Thanks to a newly developed light collection region for the collinear laser spectroscopy beam line at ISOLDE/CERN, we have successfully measured the hyperfine structures and isotope shifts from N=19 to N=32 (38,39,42,44,46,47,48,49,50,51K). From these we extracted spins, magnetic moments and changes in root mean square charge radii δleft angle r2 right angle. These nuclear observables provide information about the evolution of the proton sd-orbits as the neutron p3/2 orbit is being filled towards N=32. A clear shell effect is observed in δleft angle r2 right angle at N=28. The measured spins, magnetic moments and δleft angle r2 right angle are presented.
[en] Laser optical spectroscopy on a thermal atomic beam has been performed on the 42Ssub(1/2)-42Psub(1/2) D1 line of 38,39,41-47K. Hyperfine structure constants and isotope shifts have been measured. Magnetic moments and changes in the mean square charge radii are deduced. (orig.)
[en] To choose conditions for growth of K3WO4F monocrystals crystallization of metals in K2WO4-KF-KI and K2WO4-KF-KBr ternary systems are investigated. Triangulation along quasibinary cross-sections separates each system for two subsystems, which fusibility curves are presented as an intersection of three 2 order surfaces. Nonvariant point coordinates are refined by projection thermal analysis
[en] Highlights: ► Novel aqueous biphasic systems formed by surfactants and potassium salts are investigated. ► Solubility and tie line data are suitably correlated by means of several known equations. ► Triton X-100 and the kosmotropic salt K3PO4 entail the greatest immiscibility region. - Abstract: During the last years, the extraction of biomolecules and chemicals by means of Aqueous Biphasic Systems (ABS) has triggered a renewed interest, making it necessary to characterize fully the solubility data of this kind of system. In this study, two surfactants belonging to Triton X series (Triton X-100 and Triton X-102) are proposed as candidates to form ABS, by adding different potassium-based salts (K3PO4, K2HPO4, K2CO3, K2S2O3 and K2SO3) at T = 298.15 K. Several equations were used to fit the solubility data which were previously obtained by means of the cloud point method. The different phase forming capacities were analyzed in the light of the Hofmeister series, the Effective Excluded Volume (EEV) theory and the molar Gibbs free energy of hydration (ΔhydG). The Othmer–Tobias equation was proposed to correlate the tie-line data.
[en] Neutron-rich nuclei around 48Ca have recently attracted much theoretical and experimental interest from the viewpoint of the appearance of a new magic number, N=34, and the disappearance of the N=28 magic number around 42Si. These properties are well described by large-scale shell-model calculations with the SDPF-MU interaction, where shell evolution due to the tensor force plays a crucial role. In this contribution, we present our recent shell-model results for β-decay properties in this region. First, we have carried out systematic shell-model calculations of β-decay half-lives and neutron emission probabilities for 78 nuclei with 13 ≤ Z ≤ 18 and 2 ≤ N ≤ 34, including odd-A and odd-odd nuclei, by calculating their Gamow-Teller distributions. β-decay half-lives are one of the most easily accessible observables by experiment, and existing data covers very neutron-rich nuclei. Neutron emission probabilities are sensitive to low-lying nuclear structure. The present calculation gives an excellent agreement with experimental half-lives and β- decayed neutron emission probabilities. The calculation shows that a sort of 'pygmy' Gamow-Teller resonance develops for the decays of even-even (0+) to odd-odd (1+) nuclei and dominates observed half-lives and neutron emission probabilities. It is most likely that proton-neutron pairing make a significant contribution to this property. Second, we have calculated first-forbidden β-decay half-lives of neutron-rich K isotopes to probe nuclear structure of neutron-rich Ca isotopes beyond N=28. We have succeeded in reproducing experimental log(ft) values for the decays of 50-53 K, and have obtained useful information on shell evolution from the comparison to the data. In particular, we have identified energy levels associated with neutron excitation across the N=28 gap in 50,51Ca and a level dominated by neutron excitation across the N=32 gap in 53Ca. This document is made up of an abstract and the slides of the presentation. (authors)
[en] We present the results of experiments involving the isotopic fractionation by diffusion of K+ cations in methanol at 298 K along with supporting molecular dynamic simulations. The experiments, using glass Rayleigh fractionators filled with a methanol solution of KCl, constrain the ratio of the individual diffusivities of 41K and 39K (D41K/D39K) in methanol, and so the isotopic fractionation of K+ due to diffusion in methanol, to 0.9995 ± 0.0001. This isotopic fractionation is 25% of the fractionation resulting from K+ diffusion in water. This is consistent with published molecular dynamics simulations indicating greater hydrodynamic coupling between K+ ions and solvating methanol molecules compared to K+ ions and solvating water molecules.