The correlation of methyl tunnelling and thermally activated reorientation: II

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Abstract
For pt.I see ibid., vol.14, p.L525 (1981). It has been demonstrated that it is possible to predict methyl hopping rates in solids over a wide temperature range, from a single measurement of the methyl tunnelling frequency at low temperatures. Previous measurements, though, have been largely limited to tunnelling frequencies in excess of 100 MHz which are accessible to high-resolution inelastic neutron scattering. By exploiting the detection of weak tunnel sidebands of nuclear magnetic resonance spectra in methyl malonic acid, it is demonstrated that the theory works equally well for a system having a tunnel frequency of 68+or-2 kHz. The temperature dependences of both the proton spin-lattice relaxation time and the tunnel frequency agree well with the theory.