Experimental studies of acoustically induced birefringence

The theory of acoustically induced birefringence in liquids indicates that the birefringence should be proportional to the shear viscosity (η), the acoustic frequency (Ω/2π), and the square root of the acoustic intensity. Furthermore, the birefringence should be proportional to the square root of a dimensionless rotational translational coupling parameter (R0), a coupling parameter which also enters the theories of flow birefringence and of VH and HH depolarized light scattering. We have studied the acoustically induced birefringence of triphenylphosphite and have found the predicted dependence upon Ω,ℐ1/2 and η; in addition we find that R0 is independent of η and T, and that R0 has a value close to that obtained from flow birefringence and depolarized light scattering experiments. We have also studied the acoustically induced birefringence of solutions of large colloidal particles (gold sol); the existing theories predict that the birefringence should be linear in ℐ, and independent of Ω and η. Both previous work and ours indicate a strong Ω dependence; where previous work indicated linearly in ℐ, we find a dominant ℐ1/2 dependence together with a small term linear in ℐ; the dependence on η is still rather unclear. Our results on the gold sols are somewhat qualitative, in part because of insufficient characterization of the sols.