The magneto-luminescence spectra of the fourfold n = 1 A-exciton in ZnO up to H = 5 T are reported. The Zeeman splitting in the configuration H 11 c, k 1 c, E I c clearly demonstrat,es the influence of the k-linear energy terms allowed for the k-components perpendicular to the c-axis for 1', valence bands of the wurtzite structure. The appropriate exciton coupling matrix is calculated. From the comparison with the experimental results the A-valence band slope C = = 2 x 10 -10 eV cm is calculated.Die Magnet,olumineszenzspektren der vier n = 1 A-Exzitonenzustiinde in ZnO werden bis zu Magnetfeldern von 5 T untersucht. Die Zeeman-Aufspaltung fur die Geometrie H 11 c, k 1 c, E 1 c zeigt deutlich den EinfluB der k-linearen Energieterme fur die Komponenten des k-Vektors senkrecht zur c-Achse fur I',-Valenzbiinder von Wurtzit. Die zugehorige Exziton-Kopplungsmatrix wird berechnet. Der Vergleich mit den experimentellen Ergebnissen ergibt fur die Steigung des A-Valenzbandes C = 2 X 10-lo eV cm.
niudAluminiumhalogenid-Elektrode und der Uberspannung, die eine zur Aufrechterhaltung stabilen LochfraBes ausreichende Keimbildungsrate liefert. Zur Ermittlung dieser Lochfrat3-Uberspannung wurde einerseits eine nach Volmer berechnete Tunnelkeirnbildungsrate und anderemits die experimentell bestimmte Lebensdauer von Einzeltunneln herangezogen. Auf dieser Grundlage berechnete Werte des LochfraDpotentials stimmen gut mit MeRwerten in Chlorid-, Bromid-und Jodidl6sung iiberein. Nur der Lochfrd in Fluoridlosung ist ein Sonderfall.
Resuits of electrochemically controlled studies on the stress corrosion behavior of AIZnMg alloys in sodium chloride solutions are presented. The aim was to investigate systematically crack propagation in these alloys and its relation to metallurgical and environmental parameters. Stress corrosion cracking (SCC) is found to be a discontinuous process carried forward by anodic hydrogen embrittlement (HE). The intercrystalline nature is the result of the deformation properties of the material. Moreover, it is demonstrated that intergranular corrosion (IGC) and SCC are independent phenomena, such that metallurgical factors promoting IGC always retard the crack propagation rate.( ' ) Values of the electrode potential are on the standard hydrogen scale.
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