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Two non-first-order kinetic peaks at about 350 and 500 K appear in the thermoluminescence (TL) spectra of single-crystal and polycrystalline MgA1&04 irradiated with ionizing radiation at room temperature. Among others, emission from Cr'+ and Mn + ions are observed. TL measurements at different wavelengths indicate that the emitting centers have different recombination probabilities. Thermallystimulated-current and thermoelectric-power measurements, together with results on the TL excitation spectra with ultraviolet radiation, indicate that both processes are due to thermally released electrons from traps. The V centers also act as recombination centers leading to a complex emission band at around 4.9 eV. Experimental results and numerical simulations based on a recent1y proposed mathematical model suggest that the massive presence of lattice defects, as a result of the antisite disorder and the nonstoichiometry of synthetic spinel crystals, may have a strong influence on electron-trapping and-detrapping processes, leading to complex-kinetics TL phenomena.

It has been found in nominally p m NaCl single-crystal samples that have been either gamma irradiated, plastically deformed or quenched into liquid nitmgen from 700'C. that an additional quenching with a short residence lime at the quenching temperature ,reveals the presence of dipolar defects by means of ionic chermocumnt (ITC) measurements. This procedm dws not induce ITC signals in untreated samples. Since the occunence of divKancies and divncancy clusters in plastically deformed or quenched samples is apected. it is pointed out that gamma irradiation may also form divacancies. The fact that all the ITC spectra of the samples treated in the above-indicated ways exhibit peaks at similar temperatures also supports this view.The parallelism observed between the stored energy specba of these samples and the evolution of the ITC m a s agilinst the quenching temperature indicates that the two phenomena are related.The occurrence of dipolar def-is consistent with a previous proposal: that the stored energy release is due to the recombindon of divqcaneies with alkali halide molecules,

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A simple theoretical expression for t h e static structure factor a(&) of non-simple liquid metals is presented. The expression results from a superposition of two Ashcroft-Lekner type expressions of the interference functions of hard sphere models, by assuming that the liquid metal contains two types of clusters, each type being characterized by a set of four parameters. Calculations of a(&) for liquid Hg, Ga, Sn, and Bi are made. The theoretical results are found in good agreement with experimental data and better than those predicted from the Ashcroft-Lekner expression, in the region of interest for the well-known Ziman theory. Ein einfacher theoretischer Ausdruck fur den statischen Strukturfaktor a(&) von nicht-einfachen fliissigen Metallen wird dargestellt. Der Ausdruck ergibt sich aus einer tfberlagerung von zwei Ausdriicken vom Ashcroft-Lekner-Typ fur die Interferenzfunktionen von harten Kugelmodellen, wobei angenommen wird, daB das fliissige Metall zwei Typen von Gruppen enthiilt und jede der beiden durch eine Serie von vier Parametern charakterisiert wird. Berechnungen von a(&) fur fliissigesHg, Ga, Sn und Bi werden durchgefiihrt. Die theoretischen Ergebnisse erweisen sich als gut iibereinstimmend mit experimentellen Daten, und besser als jene, zu deren Vorausbestimmung der Ashcroft-Lekner-Ausdruck diente, im Geltungsbereich der bekannten Ziman-Theorie.