Temperature Dependence of the Pure Quadrupole Resonance Frequency and Spin—Lattice Relaxation Time in NaBrO3 at Low Temperature

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Abstract
The pure quadrupole resonance frequency of Br79 and Br81 in NaBrO3 has been measured between 4.2° and 77.3°K. The spin—lattice relaxation times have been measured between 4.2° and 16°K. The frequency measurements were compared with the Bayer—Kushida theory. While qualitative agreement with the theory is found over the entire temperature interval investigated, the theory does not fit the data in detail. The spin—lattice relaxation times were compared with the theory developed by Chang for NaClO3. If a linear or parabolic temperature dependence of the Br quadrupole frequency is used, as has been the case in all previous work, the theory can be made to agree with the data by appropriately choosing the Debye temperature. However, if the more nearly correct temperature dependence of the quadrupole frequency given by Bayer is inserted into the theory, it is found that no reasonable adjustment of the Debye temperature gives agreement. Fair agreement with the data can be obtained in this case by adjusting the velocities of the longitudinal and transverse lattice waves. Furthermore, at low temperatures the frequency dependence of Bayer leads to nearly equal contributions to the relaxation of Δm=±1 and Δm=±2 transitions, in contrast to the assumption of a linear or parabolic temperature dependence which leads to negligible contribution by the Δm=±2 transitions.