Abstract
Polarized and depolarized Raman scattering spectra have been measured for the totally symmetric stretching v 1 mode of CO2- 3 ion in a series of highly corrosive molten alkali carbonates at 1193 K. The vibrational autocorrelation function C v(t) and the rotational autocorrelation function C R(t) have been evaluated successfully from Fourier transformation of the spectra. The rotational relaxation of the CO2- 3 ion was slower than that of the NO- 3 ion in spite of the much higher temperature and an almost similar moment of inertia and molecular shape. The cation dependence of the relaxation was very small. The CO2- 3 ion showed a smaller vibrational relaxation time than the NO- 3 ion did and became considerably more rapid with decreasing ionic radius of the counter-cations. All these results, except for the cation dependence of the rotational relaxation, can be interpreted qualitatively in terms of the interionic interaction of the rotor, or oscillator, with the surrounding ions.