Fluorine and proton spin absorption and relaxation in solid ammonium heptafluozirconate

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Abstract
H1 magnetic resonance absorption in (NH4)3ZrF7 has been studied over the temperature range 20° to -196°c. A line width transition due to low activation energy reorientations of two types of NH4 + ion was observed. The fluorine absorption data give also evidence of reorientation of zirconiumfluorine complex. The transient experiment carried out at 15·3 and 22·9 Mc/sec in the same temperature interval supports the absorption results by indicating conclusively that two motions are effective in the crystal studied. The slower one is the zirconium-fluorine ion reorientation, the faster one, the reorientation of the weakly hydrogen-bonded NH4 + ions. The relaxation data exhibit strong F-H and H-F cross relaxations: at higher temperatures fluorines and protons relax essentially through the slower motion of the zirconium-fluorine complex, while at lower temperatures both spins relax through the high frequency reorientation of the NH4 + ions. The observed dynamic disorder is compatible with the Hampson-Pauling interpretation of the (NH4)3ZrF7 structure and thus supports implicitly the existence of the (ZrF7)--- complex.

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