Enhanced core polarization in (70)Ni and (74)Zn

The reduced transition probabilities B(E2;0(+) --> 2(+)(1)) of the neutron-rich (74)Zn and (70)Ni nuclei have been measured by Coulomb excitation in a (208)Pb target at intermediate energy. These nuclei have been produced at Grand Accélérateur National d'Ions Lourds via interactions of a 60A MeV (76)Ge beam with a Be target. The B(E2) value for (70)Ni(42) is unexpectedly large, which indicates that neutrons added above N=40 strongly polarize the Z=28 proton core. In the Zn isotopic chain, the steep rise of B(E2) values beyond N=40 continues up to (74)Zn(44). The enhanced proton core polarization in (70)Ni is attributed to the monopole interaction between the neutron in the g(9/2) and protons in the f(7/2) and f(5/2) spin-orbit partner orbitals. This interaction could result in a weakening of magicity in (78)Ni(50).     

AB initio method for treatment of spatially extended systems I vanishing atomic two-electron integrals

Acta Physica Hungarica - The possibility of the calculation of molecular properties on ab initio level for extended systems is investigated in a series of papers. In the first Part the effect of...     

In-beam γ spectroscopy using DIC with a radioactive Ne beam

A study of deep-inelastic and multi-nucleon transfer reactions to populate neutron-rich O, Ne and F nuclei is here presented. The reaction under analysis employed a beam of radioactive ²⁴Ne at 7.9 AMeV, provided by the SPIRAL facility at Ganil, impingin on a ²⁰⁸Pb target. The reaction products have been detected in the VAMOS spectrometer in coincidence with gamma rays measured by the EXOGAM array. Preliminary results here presented show a selectivity in the population of states of different nature.     

X-ray photoelectron spectroscopy investigations of Si in non-stoichiometric SiNx LPCVD multilayered coatings

Si nanocrystals were formed in the non-stoichiometric Si-enriched SiN_x low-pressure chemical vapor deposited (LPCVD) coatings on Si wafers treated by various modes. The coating structure as a function of technological conditions was investigated by ellipsometry and X-ray photoelectron spectroscopy (XPS) depth profiling. It was found that nanocomposites on base of SiN_x films enriched by Si have a complex multilayered structure varying in dependence of deposition and annealing parameters. Analysis of the XPS spectra and Si 2s peaks shows the existence and quantity of four chemical structures corresponding to the Si–O, Si–N states, nanocrystalline and amorphous Si. The XPS results show evolution of the chemical structure of silicon nitride and formation of Si nanocrystals. It was found:

• The LPCVD technology of nanocrystals formation allows to get enough high concentration of Si nanocrystals on different depths from the sample surface.

• The volume fraction of nanocrystalline and amorphous Si is changed with depth; this relation depends from SiN_x composition and annealing parameters.

• XPS detects these two phase compositions of Si nanoparticles in SiN_x and SiO₂ layers. The ellipsometry, HR-TEM, and XPS results are in good agreement.

Reaction of Phosphoramides with Isocyanates in PTC Conditions - Novel Method of Synthesis of Carbodiimides

Abstract

During our attempts to prepare asymmetrically substituted carbodiimides of biochemical interest we have observed that phosphoramidate-esters react under phase-transfer conditions with isocyanates giving carbodiimides.     

A new μs isomer in 136Sb produced in the projectile fission of 238U

Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed. Received: 30 March 2001 / Accepted: 18 September 2001     

An improved method for assay of vitamin C in fish feed and tissues

Summary A method was devised to assay four forms of vitamin C: L-ascorbic acid (AA), dehydroascorbic acid (DHA), ascorbate-2-mono- and polyphosphate (AMP, APP), as well as ascorbate-2-monosulphate (AMS), in sample series of different fish tissues and feed. Direct and indirect detection were combined. Sample extractions were carried out with 0.2 mol L⁻¹ sodium acetate buffer (pH 4.8) and extracts were deproteinized after different chemical or enzymatic reactions, with perchloric acid. The DHA was reduced to AA with dithioerythritol (DTE). Ascorbate oxidase enzyme was used for the detection of background and an acidic phosphatase enzyme for the hydrolysis of different phosphate esters. Ascorbate-2-sulphate was detected directly with help of coinjection of the compound. Chromatographic analysis was carried out with a single column isocratic reverse phase method. The mobile phase was an aqueous buffer of 0.04 M sodium-acetate, 0.05 mM EDTA, 0.5 mM tetrabutylammonium dihydrogen phosphate (TBA) adjusted to pH 3.76 with 85% H₃PO₄ and with 24 mL methanol added to 1000 mL. C-18 columns were used with 0.6 mL min⁻¹ flow rate at 23°C. The vitamin C forms were detected by UV absorption at 250 nm. The determination limit was 1.0–5.0 μg g⁻¹ in AA equivalent. The standard deviations were between 1–6% and depended on the concentrations of vitamin C forms and tissues. Recoveries were between 90–96% in samples. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997