Memory Effects in Confined Fluids via Diffusion Measurement

1. Introduction For bulk fluids it is always possible to establish the state of the equilibrium coexistence between vapour and liquid phases by putting these phases in contact. In contrast, the fluids confined in mesoporous matrices can reside in different quasi-equilibrium coexistence states for very long periods of time. The transition between these metastable states occurs via changes in the driving force (pressure or chemical potential, temperature of the bulk phase) or via the thermally induced fluctuations of the fluid. The latter process is generally accompanied by very large barriers in free energy and may result in the occurrence of the so-called adsorption hysteresis.