Optically Detected Electron Spin Locking and Rotary Echo Trains in Molecular Excited States

Electron spin locking, rotary echoes, and rotary echo trains have been detected for molecules in their excited triplet states by monitoring the microwave-induced modulation of the phosphorescence. The preliminary results of these studies suggest that nuclear and electron spins in ground and excited states, acoustic phenomena in molecular solids, energy transfer, spin-exchange, nuclear polarization, and a wide variety of additional processes can be optically detected, measuring as few as ${10}^4$ spins.