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Molybdenum wires were neutron irradiated at liquid nitrogen temperature and subsequently annealed up to 800 °K. The residual resistivity showed two main recovery peaks, one at 130 °K and one at 440 °K, with associated activation energies of 0.40 ± 0.04 eV and 1.23 ± 0.06 eV respectively. The activation energy increases linearly with temperature between 80 °K and 350 °K where in a rather discontinuous way a 0.25 eV higher value is reached, which remains practically constant up to 480 °K. It is suggested that the 1.23 eV stage is basically governed by the same processes as the third annealing stage in the f.c.c. metals.

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on the occasion of his 75th birthday A number of publications on the controversial problem of the vacancy migration energy in u-iron is reviewed. Positron lifetime experiments point to vacancy migration in the stage 111 range a t about 220 K. Howevcr, the corresponding vacancy migration energy of 0.6 eV is in contradiction with the value derived from other experiments e.g. self-diffusion and high voltage electron microscope irradiation experiments. Some suggestions for further research are made. Eine Anzahl von Publikationen uber das kontroverse Problem der Leerstellenwanderungscnergie in a-Eisen wird kritisch analysiert. Positronenlebensdrsuerexperimente ergeben eine Leerstellenwanderung im Bereich des Zustands I11 bei etwa 220 K. Jedoch befindet sich die entsprechende Leerstellenwanderungsenergie von 0,6 eV im Widerspruch mit dem Wcrt, der aus anderen Experimenten, z. B. Selbstdiffusion und Hochspannungselektronenmikroskopie-Bestrahlungsexperimenten, abgeleitet wird. Einige Vorschllge fur weitere Untersuchungen wcrden angegeben.