Molecular Relaxation of Binary Systems LiNO3–LiClO4, NaNO3–NaNO2, K2CO3–K2SO4

Molecular relaxation in binary systems LiNO3–LIClO4, NaNO3–NaNO2, and K2CO3–K2SO4 is studied using Raman spectroscopy. The relaxation time of ν1(A) vibrations for NO3− and CO32− anions is found to be shorter in LiNO3–LIClO4, NaNO3–NaNO2, K2CO3–K2SO4 than in LiNO3, NaNO3, K2CO3, respectively. Higher relaxation rate is explained by additional relaxation of excited vibrational states. This mechanism is associated with vibrational excitation of the second anion ( ClO4−, NO2−, SO42− ) and “production” of a lattice phonon. This relaxation mechanism is possible when the difference between the frequencies of these vibrations falls into the region of fairly high density of states of the phonon spectrum.