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Abstract:
The orientation and temperature dependences of of the deuterons in single crystals of KDCO3 were measured. The orientation dependence data are interpreted in terms of a fluctuating quadrupole coupling tensor Vfl which is compared with a model in which the jumping of the deuterons between two possible sites 1 and 2 along the hydrogen bond is considered to be the spin-relaxation determining process. From the agreement between model and experiment it is concluded that such jumps do occur in KDCO3 and dominate the deuteron relaxation rate. The prominent feature of the temperature-dependence data is a steady trend in the plot of log T1−1 vs toward steeper variation at lower temperatures. This is clear evidence that the two deuteron sites are energetically inequivalent with ΔE = 4.3 kJ/mol. The barrier between the two sites is Ea = 3.9 kJ/mol. The temperature dependence of the rate constants k1 and k2 is also inferred from the data. The combination of Vfl with the motionally averaged quadrupole coupling tensor , determined from line splittings, allowed us to calculate the quadrupole coupling tensors V1, and V2 corresponding to the two possible deuteron sites in KDCO3. The results of a similar study on tetrafluoroterephthalic acid, C6F4(COOD)2, are briefly mentioned.
