Part one of this thesis consists of two sections. In the firstsection the fluorine chemical shift of a single crystal CaF_2 has beenmeasured as a function of external pressure up to 4 kilobar at roomtemperature using multiple pulse NMR techniques. The pressure dependenceof the shift is found to be -1.7 ± 1 ppm/kbar, while atheoretical calculation using an overlap model predicts a shift of-0.46 ppm/kbar. In the second section a separation of the chemicalshift tensor into physically meaningful "geometrical" and "chemical"contributions is presented and a comparison of the proposed modelcalculations with recently reported data on hydroxyl proton chemicalshift tensors demonstrates, that for this system, the geometricalportion accounts for the qualitative features of the measured tensors.
Part two of the thesis consists of a study of fluoride ion motionin β-PbF_2 doped with NaF by measurement of the ^(19)F transverserelaxation time (T_2), spin lattice relaxation time (T_1) and the spinlattice relaxation time in the rotating frame (T_(1r)). Measurementsover the temperature range of -50°C to 160°C lead to activationenergies for T_1, T_(1r) and T_2 of 0.205 ± 0.01, 0.29 + 0.02 and 0.27 ±0.01 ev/ion, and a T_(1r)minimum at 56°C yields a correlation time of0.74 μsec. Pressure dependence of T_1 and T_2 yields activation volumesof <0.2 cm^3/g-mole and 1.76 ± 0.05 cm^3/g-mole respectively. Thesedata along with the measured magnetic field independence of T_1suggest that the measured T_1's are not caused by ^(19)F motion, but bythermally excited carriers.
Part three of the thesis consists of a study of two samples ofTh_4H_(15), prepared under different conditions but both having the properratio of H/Th (to within 1%). The structure of the Th_4H_(15) as suggestedby X-ray measurements is confirmed through a moment analysis of therigid lattice line shape. T_1 and T_2 measurements above 390 K furnishactivation energies of 16.3 ± 1.2 kcal/mole and 18.0 ± 3.0 kcal/mole,respectively. Below 350 K, T_(1r) measurements furnish an activationenergy of 10.9 ± 0.7 kcal/mole, indicating most probably more than asingle mechanism for proton motion. A time-temperature hysteresiseffect of the proton motion was found in one of the two samples and isstrongly indicative of a phase change. T_1 at room temperature andbelow is dominated by relaxation due to conduction electrons with theproduct T_1T being 180 ± 10 K-sec. Using multiple pulse techniques togreatly reduce homonuclear dipolar broadening, a temperature-dependentline shift was observed, and the chemical shift anisotropy is estimatedto be less than 16 ppm.