Cross relaxation in γ-irradiated ruby

Measurements have been made of the increase, following gamma -irradiation, in the spin-lattice relaxation rate of Cr3+ ions in ruby and of the reduction of this produced by subsequent ultraviolet irradiation. Measurements of the changes in strength of the resonant phonon scattering at approximately 6 cm-1 produced by the same treatments showed that the additional relaxation rate was proportional to the strength of the resonant phonon scattering over much of the range. It is concluded that both effects are due to Cr2+ ions and that the limiting process in the relaxation is cross relaxation between Cr3+ and Cr2+ ions. In the crystals used, the mean chromium ion separation was approximately 40 AA and the cross-relaxation time at 42K was approximately 1.2*10-4 s.