STRUCTURAL AND DYNAMICAL ASPECTS OF SOLID SULPHOLAN IN THE TEMPERATURE-RANGE 160-300 K .2. INCOHERENT QUASI-ELASTIC NEUTRON-SCATTERING STUDY

The dynamics of the sulpholan molecules in their high (I and II) and l ow-temperature (III and IV) phases is studied using the incoherent qua sielastic neutron scattering technique (IQNS). The experiments were ca rried out on polycrystalline samples using the time-of-flight time-foc ussing neutron spectrometer IN6 at the Institut Laue-Langevin in Greno ble, with a temperature ranging from 160 to 298 K. The results are com pared with the conclusions of previous NMR studies and examined in ter ms of several models. It is shown that on the 10(-11) s time-scale acc essible to the experiment, the molecular motions in the two high-tempe rature phases essentially consist of a uniaxial rotation about the two fold symmetry axis. In the low-temperature phase IV no quasielastic br oadening was observed. Conversely, in the other low-temperature phase III, restricted angular oscillations of molecules about their equilibr ium positions are responsible for a distinct quasielastic broadening o f the spectra, Another paper (paper I) deals with the structural aspec ts of the phase transitions.