Erholungsvorgänge in UV-bestrahltem Silberchlorid

The formation of defects in AgCl single crystals under UV and X-ray exposure and their thermal annealing are studied by measuring the optical density, the lattice parameter change, the X-ray Ag-reflection and by electronmicroscopical observations. Specks of crystalline silver are found to be produced at the surface of the crystals as well as in the interior. According to surface and volume darkening the isochronal annealing curves exhibit two stages. The activation energy for stage I, (0,59±0,08) eV, is suggested to be the energy for the thermal formation of electrons and Ag ₀ ⁺ -ions from Ag-aggregates. Stage II appears when the crystal is annealed in chlorine at above 523 °K. It is due to the regeneration of silver at the surface, where chlorine was able to leave the crystal during exposure.     

Excitonspektren von Silberhalogeniden und ihren Mischungen

The absorption spectra of AgBr and AgCl as well as their mixtures were investigated at liquid oxygen temperature. There are two characteristical features for exciton bands: the terms of the free atoms, and the structure of the crystal lattice. For pure and mixed crystals there exist doublets which can be derived from the terms of the free halide atoms. The wavelengths of the exciton bands shift linearly with increasing content of AgCl in AgBr. For the first band of the absorption edge this shift is 70 cm^?1 per mole percent admixture. The bands shift to a greater extent than they broaden. Thus from statistical calculations can be deduced that there is a region of about 125 anions responsible for an absorption act. The exciton bands depend considerably on thermal influences from the lattice as well as on distortions resulting from ultraviolet exposure.     

Reststrahlspektrum und Eigenabsorptionskante von CdxCa1−xO

The reflectivity of Cd_xCa_1?xO mixed crystals prepared by sintering has been measured at 300 °K from 0.2 to 47μm. The Reststrahlenbands show the expected “one-mode” behavior. By Kramers-Kronig-analysis, the longitudinal and transversal optical mode frequencies, the static and high frequency dielectric constants, the damping constants and the Szigeti-effective charges were determined in dependence on the relative admixturex of Cadmium. While the bandgap and the optical lattice frequencies vary linearly withx, the effective charge shows a deviation from linearity.     

Optische Plasmaresonanz in CdO

The plasma resonance in semiconducting CdO with different electron concentrations has been investigated by means of reflectivity measurements on thin films with metallic substrate. The results — especially the dependence of the plasma frequency on carrier density — are discussed within the framework of the classical dispersion theory. At some films peculiarities of the reflectivity have been observed which suggest inhomogeneities of the electron concentration along the layer normal.     

Gitterkonstanten- und Dichteänderung durchF-Zentren in KBr

F centers were created in KBr by additive coloration. Change of lattice parameter was determined by the X-ray diffraction method and change of mass density by a hydrostatic flotation method. Combination of these results led to a lattice expansion of 0.6 atomic volumes perF center. Using elastic approximation the microscopic dilatation around anF center is obtained.     

Residue mass plot and abundance plot: detection of isobaric interferences in DE-MALDI-TOF-mass spectra of complex polymer mixtures

Mass spectra of complex polymer mixtures often disturbed by overlapping homologue peak series have been interpreted by means of the novel techniques of the residue mass plot and the abundance plot. The model substance used for the investigations is so far poorly characterized non-ionic emulsifier Cremophor EL (polyoxyl 35 castor oil) (CrEL), a heterogeneous polyethoxylate mixture. Because of its high amount of hydrophobic and hydrophilic components, CrEL was separated into two fractions, aqueous and methanolic, by cation exchange (CCaEx) chromatography. CrEL was then subjected to delayed extraction matrix-assisted laser desorption/ionization time of flight mass spectrometry (DE-MALDI-TOF-MS). Evaluation of the mass spectra was performed by comparing the residue masses of the homologue peak series with the calculated residue masses of potential components of the excipient cationized with Na+ and K+. A number of these series are overlapping because they differ in their theoretical residue masses by about 0.05 Da. The detection of these isobaric interferences was the basic requirement for our analysis method. This goal was achieved by high mass accuracy of the measurements (obtained by internal calibration) in combination with two newly developed evaluation methods, the residue mass plot and the abundance plot. Using this combined technique, generally applicable for complex polymer mixtures, it was shown that the aqueous CCaEx fraction contains hydrophobic components such as di- and triesters of ricinoleic acid and polyethylene glycol as well as glycerol polyoxyethylene di- and triricinoleates, whereas the methanolic fraction contains hydrophilic components, mainly polyethylene glycol (PEG) and glycerol polyoxyethylene ether. Moreover, free PEG was shown to consist of PEG 800 in contrast to the value of 600 Da described so far in literature.     

Lattice contraction due to quenching in vacancies in platinum and gold

Combined measurements of lattice parameter and electrical resistivity change of platinum and gold after quenching were performed. The lattice contraction due to vacancies could be determined.     

Ionspray mass spectrometric and tandem mass spectrometric investigations of N-aliyl-N′-arylsulphonylthioureas, -isothioureas and -guanidines

Mass and tandem mass Spectrometric results for N-allyl-N′-arylsulphonylthioureas,-isothioureas and -guanidines using the pneumatically assisted electrospray (ionspray) technique are presented. The mass Spectrometric experiments show dominant quasi-molecular peaks of the monomers and signals of dimers and, more weakly, fragments. Full mass spectra are available from amounts below 500 fmol, indicating a high sensitivity. By tandem mass spectrometry of the protonated molecular ions and their fragments (sequential dau ghter-ion scanning) and using the chlorine and bromine isotope patterns, the fragmentation pathways were elucidated.     

Gitterfehlordnung in KCl mit Farbzentren

Color centers were created in KCl single crystals by additive coloration and X-irradiation at room temperature. Change of lattice parameter was determined by an X-ray method and change of mass density by a hydrostatic flotation method. Combination of these results, together with optical absorption measurements, led to the following results: F centers in additively colored KCl are Schottky defects. They cause a lattice expansionΔ v/v=0.58 perF center.F centers in X-irradiated KCl are parts of Frenkel defects. During irradiation atoms are displaced to interstitial lattice sites. The volume expansion isΔ v/v=1,15 perF center.