ADSORPTION OF DIMETHYL-SULFOXIDE TO THE LIQUID VAPOR INTERFACE OF WATER AND THE THERMOCHEMISTRY OF TRANSPORT ACROSS THE INTERFACE/

Resonantly enhanced surface second harmonic generation has been used t o measure the adsorption isotherm of dimethyl sulfoxide (DMSO) at the liquid/vapor interface of water. The Langmuir model of interfacial ads orption was used to model the data allowing determination of -11.8 (si gma = 1.2) kJ/mol for the Gibbs free energy of adsorption of DMSO to t he liquid/vapor interface of water at 293 K. This value of the adsorpt ion energy is combined with data obtained from the literature to yield a complete thermodynamic characterization of a model potential energy surface for the transport of DMSO across the liquid/vapor interface o f water. Some implications of this potential energy surface on the kin etics of mass transport are presented.