Department of Chemistry, University of California, Santa Cruz, CA 95064
The orientational dynamics of several diatomic molecules of varying dipole moments adsorbed at different locations at the interface between water and carbon tetrachloride are studied using molecular dynamics computer simulations. The dynamics are compared with those in bulk water and in bulk CCl4. A nonpolar solute experiences a lower effective viscosity and faster rotation at the interface than in either of the two bulk phases. Highly polar solutes have the opposite behavior: they experience higher effective viscosity and slower rotation at the interface than in either of the two bulk phases. A possible explanation for these observations in terms of the structure of the interfacial solute-water complex is presented. It is also found that for the solute molecules considered here, where nonpolar reorientation dynamics are quite isotropic, the out-ofplane rotation of a highly polar solute is faster than the in-plane rotation.