Orientation dependence of the23Na nuclear quadrupole spin-lattice relaxation in sodium nitrate

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Abstract
The orientation dependence of W2/W1 has been measured for 23Na in sodium nitrate at room temperature, using a steady state double resonance technique. The following ratios of the components were found: M1313/M1111=0.850+or-0.015, M3333/M1111=0.822+or-0.016, M1113/M1111=-0.120+or-0.018, M1123/M1111=0.142+or-0.017. Using symmetry arguments it is shown that M1123 should be zero in the coordinate system. The reason for the discrepancy between experiment and theory is not known. The values are compared with those obtained by Niemala (1967) at 77 K using a pulse technique. The results of a simple point charge calculation which takes into account only nearest neighbour atoms agree remarkably well with experiment. It is shown that the ratios of the M components are determined more by the configuration of nearest neighbour atoms than by the details of the lattice vibrations.