Influence of Ultrasonic Energy on the Relaxation of Chlorine Nuclei in Sodium Chlorate

Abstract

An investigation of the direct and indirect thermal relaxation processes of ${\mathrm{Cl}}^{35}$ in a single crystal of NaCl${\mathrm{O}}_{3}$ has been made by using pulsed techniques. The temperature dependence of the indirect process has been measured at four temperatures ranging between room temperature and liquid nitrogen temperature. The experimental results are in good agreement with the theoretical results of Chang.The direct process has been studied by introducing into the crystal ultrasonic energy at a frequency equal to the transition frequency between the two quadrupolar energy levels of the ${\mathrm{Cl}}^{35}$ nucleus. The agreement between the theoretical dependence of the direct-process relaxation time as a function of the energy density of the transition-frequency lattice vibrations is poor.The experiment, as done, has the basic weakness that the calculated energy density of the introduced lattice vibrations is a function of the phonon relaxation time, ${T}_{p}$, a quantity only poorly known in the most favorable cases. A different method for making the same type of study independent of the phonon relaxation time is discussed.