Vibrational Spectra of U1‐Centres in KI

U1‐centres in KI have local mode absorption bands in the region of 700 cm−1 and an in‐gap absorption band at 86.7 cm−1. The absence of any splitting in the main line (718cm−1) indicates centres of cubic symmetry (Td). The main line is accompanied by phonon sidebands. One of the strongest sidebands, 89 cm−1 above the main line, may be correlated with the directly excited phonon in the far infrared at 86.7 cm−1.