Density is one of the fundamental properties that determines the chemical and physical behavior of a liquid. Remarkably little is known regarding the density of liquids in confinement, particularly when the confinement is on the scale of a few molecular diameters. In both experiments and simulations, the key issue in the measurement of density in confinement is the inability to define the volume of the liquid. We demonstrate that the optical Kerr effect (OKE) reduced spectral density (RSD) of benzene can be used to determine the density of this liquid. Simulations show that in empirical fits of the RSD to the sum of a Bucaro-Litovitz function and an antisymmetrized Gaussian (AG), the characteristic frequency of the AG function is indicative of density and its width is indicative of temperature. Application of this method to benzene confined in porous sol-gel glasses demonstrates that this liquid is densified, with increasing confinement leading to a higher degree of densification.

Measuring liquid density using optical Kerr effect spectroscopy

253rd National Meeting (2017)

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