Pu and Am sorption to the Baltic Sea bottom sediments

Sorption of Am and Pu isotopes to bottom sediments of the Baltic Sea has been studied under natural and laboratory conditions. Data obtained from sequential extraction, sorption of Am(III), Pu(IV) and Pu(V) as well as oxidation state distribution experiments have shown that Pu(V) sorption mechanism includes a very fast Pu(V) reduction (reaction rate ≤ 2.33 × 10^?3 s^?1) to Pu(IV) by humic substances and/or by Fe(II) to Pu(IV) and partly to Pu(III). Following reduction Pu isotopes were bound to various components of bottom sediments via ion exchange and surface complexation reactions and a slow incorporation into the crystalline structure of Fe minerals. Kinetics experiments showed that the sorption of Pu(V), Pu(IV) and Am(III) to bottom sediments from natural seawater was controlled by the inert layer diffusion process.     

Thermal properties and the structure of amorphous Sb2Se3 thin film

The amorphous Sb₂Se₃ film with a thickness ~0.9 µm was prepared by thermal evaporation and its composition was confirmed using an energy-dispersive X-ray analysis. The amorphous state was checked by an X-ray diffraction analysis. The optical gap E _g ^opt was determined to be 1.32 eV. The glass transition temperature could not be found by either a differential scanning calorimetry or a thermomechanical analysis. The film was crystallized and characterized using the quasi-isothermal method. The temperature dependence of the isobaric heat capacity was raised monotonously and no drop over the course of the crystallization was observed. The temperature-modulated thermomechanical analysis determined a temperature T = 133 °C which can be assumed to be the temperature of the structural reorganization beginning. Raman spectra of amorphous Sb₂Se₃ revealed that the vibrations of both the amorphous and crystalline phase are close to one other. Raman scattering revealed that both the short and the medium-range order of amorphous and crystalline phases are similar.     

The scattering of thermal He atoms at ordered and disordered surfaces

The use of thermal energy atom scattering (TEAS) as a surface investigation tool is reviewed. Specific properties of thermal He scattering, which are particularly advantageous in surface analysis, are discussed; the main causes which hampered so far the broad application of this technique to the investigation of ordered surfaces are analysed. The recent development of TEAS based on the exploitation of the large cross section for He diffuse scattering of adsorbates and vacancies is reviewed. This development extends the capabilities of TEAS to a straightforward investigation of various aspects of disordered surfaces so far hardly accessible to other methods. Examples concerning the lateral distribution of adsorbates and defects, the mutual attraction and repulsion, 2D-phase transitions, mobility and surface diffusion are given.     

Anomalous preexponential factor for hydrogen desorption from platinum single crystals?

Abnormally low values found by some authors for the preexponential for hydrogen desorption from platinum surfaces have recently been explained by an adsorbate induced change in the dynamical characteristics of the surface itself. This possibility has been investigated in the present work exploiting the Debye-Waller effect in He beam diffraction from a hydrogen covered Pt(997) surface. Essentially no dependence of adsorbate induced attenuation of the diffracted beam intensities on the primary He-beam energy has been observed. Therefore no indications have been found for changes in the perpendicular component of platinum surface vibrations due to adsorbed hydrogen. Likewise, heats of adsorption, obtained from He diffraction experiments, do not depend on the primary energy of the He beam. This result supports the obtained normal value for the preexponential factor of $\text{ca. 10}{}^{\mathrm{?2}}\text{cm}{}^2\text{atom · s}$ (Poelsema et al., Surface Sci. 111 (1981) 519).     

Thermal characterization of hair using TG-MS combined thermoanalytical technique

Four amino acids and four different hair samples were studied in order to get information about the decomposition of human hair, using combined (TG-MS) and DSC techniques. The thermal stability of the investigated amino acid samples was different. Since they contain identical functional groups (-NH₂, -COOH) some common mass/charge units were identified. However, due to their different chemical composition remarkable differences have also been obtained. The results of the investigation of the amino acids were helpful to study the thermal fragmentation of the hair samples. In our experiments, the effect of the heating rates was also studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

The high-temperature heat capacity of ThPd3 and UPd3

The enthalpy increments of UPd₃ and ThPd₃ have been measured using the drop calorimetry for temperature range (480 to 1290) K. The heat capacity curves have been derived using the simultaneous linear regression of our data and the low temperature heat capacity data from previous studies. Furthermore the Schottky contributions for UPd₃ were determined by comparing the ThPd₃ and UPd₃ heat capacity functions and correlated with the theoretical values calculated from the crystal field energy levels.     

Excited state corrections to looped adiabatic-to-diabatic transformation phases

The difference between the full revolution adiabatic-to-diabatic transformation angle, or the loop-integrated nonadiabatic coupling term, and the Berry phase is calculated perturbationally, when one or more excited states are coupled into a ground doublet. The difference is in general non-zero, but has no definite sign. A molecule distorted from a Renner–Teller situation serves as an illustration.