Light scattering and sum rules of three coexisting phases for quasiternarysolutions near the tricritical point

摘要

The upper critical temperatures (T_U) and the lower critical temperatures (T_L) were preciselydetermined for 11 quasiternary solutions of water +n-decane and +n-undecane +tert-butanol withvarious mass ratios of n-decane to n-undecane. Measurements of angular dependence of thescattered light intensity for each of the three liquid coexisting phases and each of the 11 solutionsat the middle temperatures T_m=(T_U+T_L)/2 are reported. From the light scatting data, zero-anglescattering intensities I_0and the correlation lengths ξat T_min each of phases were calculated andused to test the Griffiths sum rules. It was found that (ΔT)~(2/3)(where ΔT= T_U– L) is a goodthermodynamic field to measure the distance from the tricritical point, and the second sum isconverged to zero with a proportionality to (ΔT)~(2/3)as the system approaches tricritical point,which is in agreement with what the classical asymptotic theory predicted. However the first sumsare neither zero nor constant, they are significantly curved and unambiguously diverged as stronglyas does an individual susceptibility, which evidences that the amplitude ratios are nonclassical.