Knowledge Bank

The triplet state of the simple merocyanine dye 3-ethyl-5-(1,3-dithiolanylidene)-rhodanine, has been examined in the crystal at low temperatures by direct absorption and by optically detected magnetic resonance (ODMR) techniques. The factor group splitting is found to be small $(\sim 0.5$ $cm-1).$ Zeeman measurements indicate that the lower energy $Bu$ factor group state uses a $\pi c\ast$ spin state and the higher energy $Au$ state uses a $\pi b$ spin state. ODMR measurements on trap emission in the pure crystal shows that all three spin states are active with phosphorescence lifetimes of 13, 36 and 315 msec. ODMR transition occurs at 4.639, 1.55 and 3.09 GHz.