ION-PAIRING AS INDICATOR FOR ENHANCED MOBILITY IN THE GLASSY STATE OFHYPERQUENCHED 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 eval uated for three spectral regions of the nitrate anion reveal changes i n ion-pairing upon physical aging which are taken as indicator for enh anced mobility in the glassy state of the hyperquenched solution and f or its rapid structural relaxation toward a state of lower enthalpy an d entropy. The difference spectra further show that physical aging of this glassy state leads to increasing contact-ion-pairing, which is co nsistent with the expected lowering of the hyperquenched sample's fict ive 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 stat e is discussed in the context of beta-relaxation. We suggest that this method can be used as a simple model system for studying enhanced mob ility in rapidly quenched glasses.