LONG-TIME FLUCTUATION OF LIQUID WATER - 1/F SPECTRUM OF ENERGY FLUCTUATION IN HYDROGEN-BOND NETWORK REARRANGEMENT DYNAMICS

The power spectrum of the potential energy fluctuation of liquid water is examined and found to yield so-called l/f frequency dependence (f is frequency). This is in sharp contrast to spectra of simple liquids (e.g., liquid argon), which exhibit a near white spectrum. This indicates that there exists an extended multiplicity of hydrogen bond network relaxations in liquid water. A simple model of cellular dynamics is proposed to explain this frequency dependence. On the other hand, the cluster dynamics of argon also involves energy fluctuations of a l/f type, resulting from various relaxation processes at core and surface.