Microwave resonance absorption in ruby

Ruby samples manufactured by three different techniques were used in electron paramagnetic resonance studies at 35 and 115 GHz, at room temperature and 77°k. In contrast with the spin-lattice relaxation results of Standley and Vaughan, no significant differences were observed between vapour-phase, Verneuil or fluxedmelt samples in relation to zero-field splitting of the energy levels, linewidths, intensities of Cr-Cr pair lines or impurity spectra. Data on these parameters are given. Evidence is presented of a variation in zero-field splitting of approximately 10% in one sample, leading to a greatly increased linewidth of some transitions.