Abstract
Measurements of spin-lattice relaxation time in ruby have been made at 34 6 Gc/s by a pulse saturation method at temperatures from 1.4° to 90°K With weak concentrations the values for the first-order transitions (e.g. 22 msec at 4.2°K) are of the same order of magnitude as those reported at lower frequencies, and the variation of relaxation time with temperature is in fair agreement with theory. A successive increase in relaxation time with the order of the transition, pronounced at 1.4°K, decreases with increasing temperature, and at about 77°K a common value of about 44 μsec is obtained for all transitions. The main effects of increasing concentration are to reduce the relaxation time and alter its temperature dependence.