Knowledge Bank

The encounter with a factor group splitting in a cubic crystal is not as rare as it may be thought to be. It has been observed in solid $CO2$, $NaClO3$, $C6H12$, and possibly in $CH4$. There are numerous other opportunities for its observation. Its understanding is not so patent. It is treated here in terms of exciton theory. Such splittings will be shown to arise in the \emph{difference} in the transition probabilities for exciton transfer from a state of vibrational angular momentum to another of opposite sign along chains of translationally equivalent molecules from that along chains of translationally inequivalent molecules.