Investigation of ${\mathrm{V}}^{3+}$ Pairs in ${\mathrm{Al}}_2$${\mathrm{O}}_3$ by Phonon Frequency-Crossing Spectroscopy

An investigation has been made of ${\mathrm{V}}^{3+}$ pairs in ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ by phonon frequency-crossing spectroscopy. The crossing spectrum can be interpreted with an interaction Hamiltonian $J{\overrightarrow{\mathrm{S}}}_1·{\overrightarrow{\mathrm{S}}}_2$ and pairs have been identified with $\mathrm{}\left|J\right|=0.29\mathrm{} \mathrm{and} 1.50$ ${\mathrm{cm}}^{-1\mathrm{}}$. Pairs have been detected at concentrations ∼2×${10}^{-2\mathrm{}}$ ppm, and it is probable that concentrations ∼2×${10}^{-3\mathrm{}}$ ppm could be detected in this way.