title: New interferometric technique to evaluate the electric charge of gas bubbles in liquids.
abstract: We report a new interferometric technique to measure the electric charge at the gas-liquid interface of a bubble in a liquid. The bubble rests by buoyancy against an electrode, and an alternating electric field excites its capillary oscillations. The oscillation amplitude of the quadrupolar mode frequency is measured by the interferometer, and it is used to evaluate the electric charge. The mode frequency scales with the square root of the interfacial tension and with a -(3)/(2) power law as a function of the bubble radius. For bubbles in the millimeter diameter range in pure water, the measured negative charge scales with the square of the radius, hence, giving a constant surface charge density on the order of 1.8 × 10(-5) C m(-2), which is rather consistent with the electrophoretic values reported in the literature.
authors.affiliation: Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Università di Milano, LITA, Via Fratelli Cervi 93, 20090 Segrate, Milano (MI), Italy. mario.corti@unimi.it
authors.forename: Mario
authors.initials: M
authors.lastname: Corti
authors.forename: Marco
authors.initials: M
authors.lastname: Bonomo
authors.forename: Antonio
authors.initials: A
authors.lastname: Raudino
mesh_terms: D004560:Electricity; D005740:Gases / Q000737:chemistry*; D007368:Interferometry / Q000379:methods*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D014867:Water