Vibrational spectra of and phase transitions in caesium hydrogen sulphate

Abstract The Raman and infrared spectra of the superionic protonic conductor CsHSO 4 (CsDSO 4 ) were investigated in the 18–450 K range. Polarized single crystal Raman and infrared reflection spectra were also studied at room temperature. An assignment of bands due to internal and external vibrations is given in terms of symmetry species and approximate type of motion. The spectroscopic results, in particular the behaviour of the Raman bands as a function of temperature, are used to discuss the crystalline structures of various phases, hydrogen bonding, the type and degree of structural disorder, phase transitions and conductivity.