Exciton Structure of CrystallineK+CN−

In the ionic molecular crystal ${\mathrm{K}}^{+}$C${\mathrm{N}}^{-}$, excitonic properties characteristic of both ionic and molecular crystals are observed at different photon energies. Various molecular exciton interactions are manifested in the low-energy part of the spectrum. A resolved Davydov-type splitting is observed for the first time in an ionic crystal and is explained by a weak-interaction model. Charge-transfer excitons occur at higher energies.