Nuclear quadrupole coupling in ND4ReO4 and ND4IO4

Abstract
The temperature and pressure dependences of the 187Re nuclear quadrupole resonance frequency in ND4ReO4 are reported, and compared with corresponding data for NH4ReO4. The temperature dependence of the deuteration shift is similar to that of the pressure coefficient of the quadrupole frequency, (∂ν/∂P)T. In both ND4ReO4 and NH4ReO4, there is a rapid change in the slope of the graph of (∂ν/∂P)T vs temperature, rather than the discontinuous change reported previously; there is no significant shift in the temperature of this feature upon deuteration. It is concluded that changes in the ammonium ion rotational motion near 200 K are the result, and not the cause, of other structural changes in the crystal. The quadrupole frequency in ND4 127IO4 has been measured at room temperature.

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