Abstract
Recent improvements in the energy resolution of incoherent inelastic neutron scattering spectroscopy allow spectra in the region 0.5 μeV (micro electron volts) [0.004 cm −1] to 50 meV (milli electron volts) [400 cm −1] to be measured with a resolution batter than 10% = ΔE/E. In this range tunnelling splittings of the librational grounds fates of molecules in molecular crystals, adsorbed on surfaces and intercalated in layer structures have been observed and provide a sensitive test of models for the rotational potential. The spectra for the CH 3, group in solid CH 3-CC-CC-CH 3; CH 4 adsorbed on graphite and H 2 intercalated in C 24C s are taken as examples. Two quite different types of temperature dependence for the tunnelling splittings are seen as well as temperature dependent line widths. As yet there is no satisfactory theoretical model to explain the phenomena which are related to effects seen in low temperature proton transfer kinetics.
Published Version
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