Figure 18.

An experimental example of a film resonance. The sample consisted of a polyelectrolyte multilayer, the thickness of which was gradually increased by repeated dipping. When displayed in polar form, the data form a spiral. These authors display the load impedance rather than the complex frequency shift. The load impedance here has the unit “Rayl”, in the honor of John William Strutt, 3rd Baron Rayleigh. 1 MKS-Rayl is equal to 1 kg/(m²s). Red and black data denote results obtained with an even number of layers and with an odd number of layers, respectively. The difference occurs because anionic and cationic layers alternate. Adapted from [91].