ION-PAIRING AS INDICATOR FOR ENHANCED MOBILITY IN THE GLASSY STATE OF HYPERQUENCHED SOLUTION

FTIR spectrum of a glassy aqueous (D2O) solution of approximate to 1.0 M calcium nitrate vitrified by hyperquenching and recorded at 78 K is compared with those recorded subsequently after physical aging of the glassy film at 100, 110, 120, and 130 K. FTIR difference spectra evaluated for three spectral regions of the nitrate anion reveal changes in ion-pairing upon physical aging which are taken as indicator for enhanced mobility in the glassy state of the hyperquenched solution and for its rapid structural relaxation toward a state of lower enthalpy and entropy. The difference spectra further show that physical aging of this glassy state leads to increasing contact-ion-pairing, which is consistent with the expected lowering of the hyperquenched sample's fictive temperature. The influence of temperature and/or time of physical aging is investigated and the spectral changes are quantified by curve-fitting. The influence of cooling rate on mobility in the glassy state is discussed in the context of beta-relaxation. We suggest that this method can be used as a simple model system for studying enhanced mobility in rapidly quenched glasses.