Damping of a crystal oscillator by an adsorbed monolayer and its relation to interfacial viscosity

Abstract

The acoustic impedance of a monolayer adsorbed on the surface of a resonating quartz microbalance produces a shift in both the frequency and vibrational amplitude of the oscillator. The relation between acoustic impedance and fluctuations in film momentum is rigorously derived via the fluctuation-dissipation theorem within the context of two-dimensional fluid mechanics. The calculations reveal that the film-substrate interfacial viscosity can be deduced from measurements of acoustic impedance.