Synchrotron-radiation-based perturbed angular correlations used in the investigation of rotational dynamics in soft matter

A new method, synchrotron-radiation-based perturbed angular correlations, was applied to study rotational dynamics of Mössbauer atoms in soft condensed matter, using incoherent nuclear resonant scattering of synchrotron radiation. A theory was developed that describes the correlations for the scattering by an ensemble of randomly oriented spins under the influence of rotational relaxation. In a feasibility study a molecular glass former doped by probe molecules was investigated above the glass transition up to the normal liquid state. A comparison of the obtained rotational relaxation rates with data from dielectric spectroscopy shows that the probe molecules reproduce the dynamics of the glass former.