Temperature of Multibubble Sonoluminescence in Water

Abstract

Sonoluminescence (SL) spectra were collected from water doped with several organic liquids at low concentrations. Most of the organic substances studied show emission from C2 and an overall decrease in the intensity relative to SL from pure water. This decrease is due to the consumption by the organic substrates of hydroxyl radicals and other incipient emitting species produced during sonolysis. Small concentrations of carbon disulfide do not lead to emission from C2 but do cause an increase in SL intensity across the spectral window, most likely due to its own fluorescence. Carbon tetrachloride does not change the intensity of water sonoluminescence but does exhibit C2 emission. This indicates that the dissociation of carbon tetrachloride inside the cavitation bubble is independent of the products of water sonolysis. Benzene shows the strongest C2 emission and was studied in the greatest detail. The emission of excited-state C2 arising from the sonication of benzene/water mixtures at 20 kHz was used to determine an effective emission temperature during cavitation in water. Interband analysis of the two C2 bands observed during irradiation of water/benzene mixtures at 278 K under Ar indicates an emission temperature of 4300 ± 200 K.