Enrichment of Zintl cluster ions

Compound cluster ions of heavy post-transition atoms (In, Pb, As, Sb, Bi) are enriched by electron induced dissociation if they are analogous to the Zintl polyanions Pb ₅ ^2? and Pb ₉ ^4? with respect to the atom and valence electron number.     

Speciation of Se, Fe and Zn in Human Milk Whey: The use of Instrumental Neutron Activation Analysis (INAA) to corroborate element profiles measured with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

In human milk trace elements normally exist in a form which can easily be absorbed by the newborn infant. For investigations of the bioavailability of trace elements it is necessary to carry out a speciation analysis of the elements of interest. An independent analytical method has been used for the quality control of the shape of the element profiles obtained from the speciation analysis of Se, Fe and Zn in individual samples to human milk whey after chromatographic separation. For the element detection in the untreated milk fractions Instrumental Neutron Activation Analysis (INAA) was chosen as the reference method. Element distribution patterns have been obtained with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) using on-line digestion of the fraction, reduction and hydride formation of Se (T-mode). Prior results are compared with those obtained by means of element detection in the untreated fractions (U-mode) with ICP-AES. The elution profiles of Se, Fe and Zn in human milk whey obtained by means of ICP-AES detection using the T-mode show good agreement with the distribution patterns obtained with INAA. Recoveries of 103% for Fe, 86% for Zn and 87% for Se were obtained. The element distribution patterns of Fe and Zn obtained with ICP-AES speciation using the T-mode also show good agreement with those obtained by means of ICP-AES using the U-mode.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday.     

Investigation of electron irradiated iron alloys and nickel

SR experiments were performed on electron-irradiated magnetic samples. In dilute iron alloys, the isolated vacancy (30 MHz line) was observed up toT _A (annealing temperature) = 200 K. Above this temperature a new line (30 MHz +v), assigned to vacancy-impurity pairs, was found in some alloys. The frequency shiftv and the annealing behaviour of the new line are characteristic for each impurity. In electron-irradiated Nino newSR line was observed.The financial support of the Bundesministerium für Forschung und Technologie is gratefully acknowledged.     

Impurity-defect configurations in ion-irradiated copper studied by the DPAC-technique with111In

The structure and dynamics of lattice defects in copper are investigated. The defects have been produced by irradiation with heavy ions of 350 keV between 85 K and 300 K. Three different defect configurations are distinguished by the time differential perturbed angular correlation technique (DPAC) with¹¹¹In as radioactive probe. Their electric quadrupole coupling constants _Q =e ² Qq _zz /h are _Q1=116(2)MHz, _Q2=181(3)MHz and _Q3=52(1)MHz. The defects characterized by _Q1 and _Q2 are observed in the temperature range of recovery stage III. The appearance of _Q3 is closely correlated with recovery stage V. The symmetry axis of the electric field gradient associated with this defect-¹¹¹In configuration points along a crystallographic 111 direction. We attribute this defect to a planar faulted loop, presumably of vacancy type. The influence of irradiating particles and dose on the defect configurations is analyzed.     

Diffusion of positive mouns in nickel and iron

The depolarization rate for spin polarized ⁺ particles implanted into high purity polycrystalline nickel and iron samples were studied as a function of temperature in zero external field. In nickel a rapid decrease of the depolarization rate above 300 K was found. Assuming an Arrhenius behaviour, an activation energy of E_a=173 meV was determined. In iron it was not possible to fit the data with a simple Arrhenius law. At least two different slopes can be observed in an Arrhenius plot with E_a=(124±35) meV and E_a=(19±2) meV, respectively.     

Infrared multiphoton excitation of refractory metal clusters

Photoexcitation and photoionization experiments on small Tungsten and Niobium clusters were performed with a Q-switched Nd:YAG laser (1064 nm) and a reflectron type time-of-flight mass spectrometer. For low laser fluences the monomer and very small clusters do not show up in the mass spectra. Furthermore, the detected cluster ions show very asymmetric peak shapes caused by delayed ionization (thermionic emission). For high photon fluences photoions with up to charge state +3 could be detected.