Dynamical universality in a critical mixture of a nonionic micellar solution

The decay rate of critical fluctuations in a nonionic micellar solution of tetraethylene glycol n-decylether (${\mathrm{C}}_{10}$ ${\mathrm{E}}_4$) in water has been investigated very close to its critical point of mixing from the time-dependent correlation function of scattered light. We find the scaled decay rate ${\mathrm{\Gamma }}_{\mathit{c}}^{\mathrm{*}}$ (=[6πη(T)/${\mathit{k}}_{\mathit{B}}$T](Γ-${\mathrm{\Gamma }}_{\mathit{B}}$)/${\mathit{k}}^3$) for ${\mathrm{C}}_{10}$ ${\mathrm{E}}_4$ in water obeys a universal function over the range from a scaled variable of kξ≃0.3–26, where ${\mathrm{\Gamma }}_{\mathit{B}}$ is the noncritical background contribution. Our experimental findings suggest that the micellar solution of ${\mathrm{C}}_{10}$ ${\mathrm{E}}_4$ in water should belong to the static and the dynamical universality class as a fluid, in conjunction with our previous works [K. Hamano et al., Phys. Lett. A 150, 405 (1990); J. Chem. Phys. 94, 2172 (1991).