Nonexponential behavior near the critical point of an ionic micellar system

The coexistence curves of the system dodecylammonium chloride + water + KCI have been obtained for different salt concentrations. We found that the as ymptotic behavior of the order parameter can be describe using extended sca ling and the usual Ising value for the beta = 0.325 exponent. The static li ght scattering data for the critical composition are also compatible with t he Ising value,nu = 0.63. Dynamic light scattering results have been obtain ed near the liquid-liquid critical point. The col I elation functions have been found to be single-exponential for temperatures well above critical, w hile a second decay process at longer times becomes evident for T - T-c < 4 K. These correlation functions can be fitted to the sum of two exponential functions. The diffusion coefficient associated with concentration fluctua tions has been calculated from both relaxation modes. It has been analyzed in terms of the predictions of the mode-coupling theory. These results, tog ether with correlation length and viscosity data, are in good agreement wit h the calculations.