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[en] The ground states of magnesium isotopes exhibit intruder configurations with the pf shell being populated before the sd shell is complete. In the transition to this ''island of inversion'' the nuclear charge radii extracted from isotope-shift measurements should clearly indicate a structural change, expected to happen in the step from 30Mg to 31Mg. The magnesium isotope shifts were measured by collinear laser spectroscopy combined with either β-decay asymmetry detection after optical pumping or fluorescence detection. Isotope shift extraction became possible only after a thorough understanding and simulation of the observed line shapes of the β-asymmetry spectra and could be demonstrated for the first time. The 24-32Mg charge radii are presented, and comparisons with the trends predicted by models are made.
[en] The island of inversion is commonly regarded as an island of deformation. Yet, the transition to a deformed configuration in the neutron-rich and neutron-deficient isotopes of magnesium is not well understood. This problem cannot be addressed by quadrupole-moment measurements due to nuclear spins 0 or 1/2 of the key isotopes. Experimental evidence from reaction studies and ground-state properties of 31,33Mg are consistent with considerable prolate deformation in the neutron-rich isotopes. The structural changes in the neutron-deficient isotopes may originate from clustering, in a way similar to neon. However, in order to obtain a consistent picture of the evolution of the nuclear shape along the magnesium chain one has to measure a quantity accessible for all isotopes (odd and even) with the same experimental technique. Accordingly, a measurement of the rms charge radii of 21-32Mg is presented for the first time with emphasis on the new method for isotope-shift measurements based on combining fluorescence detection with β-detection.
[en] The evolution of self-consistent beyond-mean-field techniques (BMF) based on the Gogny interaction to better describe nuclear spectra is presented. In particular, different implementations of symmetry restorations and configuration mixing within the generator coordinate method are discussed. Finally, the results for excitation energies in the magnesium isotopic chain from N = 8 to N = 28 are provided as an example of the performance of those different many-body methods. (orig.)
[en] This report describes the work carried out on the isotopic analysis of magnesium using Varian Mat model CH-5 mass spectrometer having a thermionic source. When magnesium was analysed by loading the samples in the nitrate form, there was significant isotopic fractionation and consequent variation in isotope ratios as a function of time. After examining the properties of several magnesium compounds, magnesium chloride was chosen as a suitable matrix for the isotopic analysis. It was found that if well defined filament temperature conditions were maintained, magnesium chloride gave rise to negligible isotopic fractionation and isotope ratios were invariant over a period of time. Conditions of magnesium isotopic analysis were thus standardized on this basis. In order to obtain absolute isotope ratios from the measured values, mass discrimination factor (mdf) was determined for this mass region. (author)
[en] High-precision mass measurements have been performed on the exotic magnesium isotopes 29-33Mg using the MISTRAL radiofrequency spectrometer, especially suited for very short-lived nuclides. This method, combined with the powerful tool of resonant laser ionization at ISOLDE, has provided a significant reduction of uncertainty for the masses of the most exotic Mg isotopes: a relative error of 7 x 10-7 was achieved for the weakly produced 33Mg that has a half-life of only 90 ms. Moreover, the mass of 33Mg is found to change by over 250 keV. Verifying and minimizing binding energy uncertainties in this region of the nuclear chart is important for understanding the lack of binding energy that is normally associated with magic numbers. (orig.)
[en] The rolling of evaporated /sup 24/ Mg, /sup 25/ Mg, and /sup 26/ Mg foils from an initial thickness range of 200 to 300 μg/cm2 down to an ultimate thickness of 60 μ/cm2 or less is described. Roll pass reduction, pack thickness and surface conditions are the main factors in the successful preparation of these foils
[en] We have defined the parameterization for Mg and made calculations on magnesium compounds (molecules, ions, and radicals) for which measured values exist for /triangle/H/sub f/298 and the geometrical parameters. The ionization potentials were derived for compounds with closed shells from Coopman's relation. The calculations indicated that all the radicals MgX have the 2Σ structure, i.e., the unpaired electron is in a nondegenerate σ level
[en] The effect of magnesium hydride on the corrosion behavior of an as-cast AZ91 alloy in 3.5 wt.% NaCl solution was investigated using gas collection method and potentiostatic test. The Pourbaix diagram of Mg-H2O system was built using thermodynamic calculation. It was possible that magnesium hydride could form in the whole pH range in theory. The experimental results showed that at cathodic region, magnesium hydride formed on surface, which was the controlling process for the corrosion behavior of AZ91 alloy; at anodic region and free corrosion potential, magnesium hydride model and partially protective film model, monovalent magnesium ion model and particle undermining model were responsible for the corrosion process of AZ91 alloy
[en] The isotope shift in the Mg I transitions lambdalambda 5167, 5172 and 5183 A (3s3p3P-3s4s3S) and lambda 5528 A (3s3p1P-3s4d1D) has been measured for the isotopes 24Mg, 25Mg and 26Mg. The measurements were carried out with separated isotopes using a scanning Fabry-Perot interferometer. (Auth.)