CRITICAL CASIMIR FORCES BETWEEN SPHERICAL-PARTICLES IN FLUIDS

Long-ranged correlations in a fluid close to its critical point T-c ca use distinct forces between immersed colloidal particles and the conta iner walls. We calculate such a force and its temperature dependence f or the generic case of a spherical particle located at a distance D fr om a planar wall and find that the force attains a maximum at a temper ature T-max(D) above T-c, which facilitates quantitative experimental tests. The corresponding effective pair interaction between the colloi dal particles themselves, potentially leading to aggregation, is also discussed.