CHEMICAL GENERATION OF ACOUSTIC-WAVES - A GIANT PHOTOACOUSTIC EFFECT

An anomalous photoacoustic effect is produced when a suspension of car bon particles in water is irradiated by a high-power, pulsed laser. Th e photoacoustic effect has an amplitude on the order of 2000 times tha t produced by a dye solution with an equivalent absorption coefficient and gives a distinctly audible sound above an uncovered cell. Transie nt grating experiments with carbon suspensions show a doubling of the acoustic frequency corresponding to the optical fringe spacing of the grating. The effect is thought to originate in high-temperature chemic al reactions between the surface carbon and the surrounding water.