Observation of Dipolar-Induced Spin Dephasing in Ionic Solids Using Coherent Optical-Microwave Spectroscopy

The observation of spin dephasing in an ensemble of dipolar coupled $A$ and $B$ spins is reported. In CaO crystals, the $A$-spin species are photoexcited $S=1\mathrm{}$, ${F_2}^{2+}$ centers and the group of $B$ spins consists of $S=\frac{1}{2}$, $F^{+}$ centers. Measurements were made at different temperatures and magnetic field strengths with use of coherent optical-microwave spectroscopy. For the first time, the results show that the $A$-spin dephasing is influenced by exchange narrowing in the $B$-spin ensemble.