A simulation approach to vibrational dynamics of the OH− ion in molten LiOH

A new simulation approach to vibrational dynamics of molecules and ions in liquids is presented. The method is concerned with calculation of the time-dependent many-body vibrational potential of an oscillator reflecting the liquid structures, where frozen field, local mode, and one-particle potential are assumed. The equation of motion is solved for this time-dependent potential to include the dynamic effect on the resultant vibrational spectra. The simulation well reproduced the isotropic Raman spectrum of the OH− ion in a LiOH melt. The peak shift, the band broadening, and the asymmetric shape which are generally found for the liquid state spectra could be interpreted satisfactorily. The analysis showed that inhomogeneous broadening as well as motional narrowing plays an essential role in the vibrational dephasing. Fluctuation of the field on the oscillator and, hence, of the instantaneous transition frequency is large and very fast. The detailed relevant molecular processes are also discussed.