Picosecond dynamics from lanthanide chloride melts

The picosecond dynamics of molten lanthanide chlorides is studied by means of vibrational spectroscopy. Polarized Raman spectra of molten LaCl3, NdCl3, GdCl3, DyCl3, HoCl3 and YCl3 are fitted to a model enabling to obtain the times of vibrational dephasing, tν and vibrational frequency modulation tω. Our aim is to find possible sensitive indicators of short-time dynamics. It has been found that all lanthanide chlorides exhibit qualitative similarities in the vibrational relaxation and frequency modulation times in the molten state. It appears that the vibrational correlation functions of all melts comply with the Rothschild approach assuming that the environmental modulation is described by a stretched exponential decay. The evolution of the dispersion parameter α indicates the deviation of the melts from the model simple liquid and the similar local environment in which the oscillator is placed and with which it is coupled. The “packing” of the anions around central La3+ cation seems to be the key factor for the structure and the dynamics of the melts. The results are discussed in the framework of the current phenomenological status of the field.

► Study of the picosecond vibrational dynamics of a series of rare earth molten chlorides.
► The breathing (stretching) νs mode has been used as probe of the vibrational dynamics.
► The vibrational correlation functions comply with the Rothschild approach.
► The dispersion parameter evolution with Ln3+ radius indicates strongly interacting system.
► “Packing” of Cl− anions is the key factor for structure and dynamics of these melts.