Discontinuous behavior of Rayleigh relaxation in supersaturated aqueous NH₄H₂PO₄ solution

The algorithm of Rayleigh intensity correlation is employed for the elucidation of relaxation time constants of the aqueous NH₄H₂PO₄ solution with various concentrations. The result shows that there is a discontinuous (abrupt) increases in the relaxation time constant as the super-saturation state is reached. This quantity, the relaxation time constant, therefore, can be an order parameter. Also discussed is the dependence of the relaxation time constant on the aggregation number n in (H₂PO₄⁻)n. This dependence is complicated and may be crucial in understanding the aggregation process in the supersaturation state.