Dynamical Quadrupole Interactions
نویسنده
چکیده
The nuclear quadrupole interaction (NQI) at the site o f 18,Ta in HfD2 has been investigated by time differential perturbed angular correlation measurements. Below 290 K the NQI is static within a 300 nanosecond time window. Above 290 K dynamic effects related to the diffusion of deuterium atoms start to appear, which have been analyzed in terms o f a 3-state stochastic model. Between 345 K and 500 K the jump diffusion o f deuterium has an activation energy E.d = (0 .3 3 i§ |) eV. At higher temperatures the relaxation spectra suggest that transitions occur, first to the <5-phase, then to the a-phase o f the hafnium-deuterium system. At 600 K the mean residence time between jumps is o f the order o f 2 nanoseconds. First measurements with HfH2 show an isotope effect compatible with the prediction o f the classical rate theory for over-barrier diffusion.
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