Nuclear probes for investigating radiation damage

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Atomic nuclei or elementary particles, produced by particle accelerators or nuclear reactors, are employed as nuclear probes, or so-called observer atoms, which provide information about their local surroundings on an atomic scale. The study of static and dynamic properties of defects with these radioactive probe atoms is performed via the hyperfine interactions. They occur between the nuclear electromagnetic moments of the probe atoms and the electromagnetic fields in their surroundings. From the interaction parameters the desired information on the solid state with reference to the probe atom is obtained. For example the structural arrangement and chemical nature of the neighboring atoms, the local magnetic and electric fields, the magnetic state of the probe atom, the binding inside the host matrix, the vibrational state and diffusion properties, and, in particular, information on the existence of intrinsic defects, i.e. self-interstitials and lattice vacancies, and extrinsic defects, i.e. impurity atoms at substitutional or interstitial lattice sites. Thereby, in most cases, information on defect complexes is obtained in which the radioactive probe atom is a constituent. The main emphasis is laid on the results of two probe techniques, Mössbauer effect and PAC/PAD. In addition a brief survey of other techniques, such as β-NMR, muon-spin rotation and blocking using radioactive emitter atoms, is given. Microscopic details of defect centres and impurity dynamics are discussed, with attention shifting from metallic systems and their annealing stages to defect centers in semiconductors.