Approximation of the theory of stochastic perturbations of angular correlations for fluctuating distributions of electric quadrupole interactions

The perturbation of angular correlations by a fluctuating distribution of electric quadrupole interactions has been calculated with Blume's stochastic theory for an ensemble of 10 states differing in magnitude and orientation of an electric field gradient as a function of the fluctuation rate w for different values of the fluctuating and the static components of the distribution. By fits to the calculated spectra it was shown that for fast fluctuations, w ≥ 5 ω0/2π, the relaxation effects caused by a fluctuating distribution can be well approximated by a single relaxation parameter λ, independent of the relative magnitude of the fluctuating component. For slow fluctuations, w < ω0/2π, a single relaxation parameter is a reasonable approximation only if the fluctuating component of the interaction exceeds the ensemble average. Otherwise the jump rates and activation energies are seriously underestimated. These conclusions are supported by a 111Cd PAC study of the hydrogen dynamics in HfV2H1.78. (orig.)