Evans hole in internal modes IR spectrum of ions in (NH4)3WO3F3 crystal

Infrared absorption of (NH4)3WO3F3 compound has been studied. Profile of asymmetric band in 600–1000 cm−1 range associated with polar W–O vibrations of WO 3 F 3 3 - ions is explicable on the basis of multi-oscillatory dynamics with account of damping. Complex profile with Evans holes proves that internal modes of WO 3 F 3 3 - anions in the fluorine–oxygen octahedron interact due to the effects of the local field.