Neutron quasielastic scattering study of SH− reorientation in rubidium hydrosulfide in the intermediate temperature trigonal phase

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Abstract
The reorientation of (SH)−ions in the trigonal phase of RbSH has been investigated by neutron quasielastic scattering at 373 and 393 K. The quasielastic peaks show a distinct two-component (elastic and broadened) structure, the behavior of which is used to establish that the ions are reorienting between two equilibrium sites (presumably by 180° flips along the trigonal axis) with average times between reorientation of 5.4 ± 0.4 psec and 4.0 ± 0.4 psec at 373 and 393 K. Mean square amplitudes of hydrogen vibration are determined from the momentum transfer dependence of the total intensity, and found to be higher than that found in the high temperature fcc phase, even though the rate of reorientation is an order magnitude faster in the cubic phase.