Measurements of Sonoluminescence from Pure Liquids and some Aqueous Solutions

An exhaustive study of sonoluminescence has been made at a frequency of 16.5 kc/s. The temperature dependence of the luminescence from 15 pure liquids and some aqueous solutions has been determined in the range 4°C to 80°C. The intensity of luminescence was correlated with various parameters; the best correlation was found with (surface tension) 2 /(vapour pressure). Photographs have been taken showing that sonoluminescence generally occurred as a single discrete flash once every sound cycle. This flash appeared to occur within a tenth of a period from the sound pressure minimum with non-volatile liquids like water; with volatile liquids, the flash apparently occurred shortly before or at the sound pressure maximum. Sometimes a secondary flash occurred shortly before or after the main flash. No sonoluminescence was detected from any liquid when the cavitation bubbles collapsed, i.e. shortly after the sound pressure was a maximum. The results would appear to substantiate the theories that sonoluminescence is caused by electrical microdischarges occurring within the cavitation bubbles and by the photochemical recombination of dissociated molecules at the nascent surfaces of these bubbles.