Fluorescence in thin liquid films

The fluorescence properties of Rhodamine B in thin liquid films, formed from a number of anionic, cationic and non-ionic surfactant solutions, were investigated. Laser excitation was used and the emission was monitored over a period of time. Drainage profiles with light and dark fluorescence fringes were recorded with plane-polarized radiation. Change of polarization caused profound changes in the appearance of the profiles. The distribution of dye molecules between surfaces of the film and its interior was assessed and found to be related to the speed of film drainage. Expressions were established for the relation between fluorescence fringes and film thickness at different orientations of the film surface to the emission measurement direction.