Nuclear quadrupole spin-lattice relaxation in solids

Abstract

Nuclear quadrupole spin-lattice relaxation in solids has been investigated using pulsed nuclear induction techniques. By selective excitation of the quadrupolar spin system, several new modes of relaxation are observed. Measurements of these modes are used to determine the individual transition probabilities W 1 and W 2 associated with Δ m = ± 1 and ± 2 quadrupole spin-lattice relaxation. W 1, W 2, and the spin-lattice relaxation time T 1 of the Cl 35 pure quadrupole resonance in p-C 6H 4Cl 2, KClO 3, and NaClO 3 have been measured in the temperature range 77–300°K. The B ayer theory of quadrupole spin-lattice relaxation is applied to p-C 6H 4Cl 2 to calculate W 1 and W 2. From the B ayer theory and the separate measurement of W 1 and W 2, information is obtained about the lifetime of excited torsional states and the mode of torsional oscillation which provides the dominant relaxation contribution in p-C 6H 4Cl 2. Measurements of the spin-lattice relaxation in NaClO 3 and KClO 3 are compared with C hang's theory of quadrupole relaxation. The experimental results suggest that the model used by C hang to describe the fluctuating internal electric field gradient in NaClO 3 responsible for the Cl 35 relaxation is inadequate.