Moessbauer spectroscopy to investigate jump mechanisms on an atomic scale: Fast diffusion studies

The fast diffusion of transition-metal impurities in metals and semiconductors provides us with a challenging research field, because the jump frequencies and the concentration of the 'diffusion vehicles' (probably interstitials) contributing to the fast diffusion are always close to the detection limit of Moessbauer spectroscopy. Therefore, several new experimental set-ups have to be developed in order to achieve a direct observation of the fast diffusing vehicles and to study the jump mechanism on an atomic scale. High temperature UHV-furnaces and the in-beam Moessbauer spectrometers, which have been constructed in different institutes in different countries, are introduced and the new experimental results obtained by these apparatus are presented