SONOLUMINESCENCE, SONOCHEMISTRY, AND SONOPHYSICS

Recent measurements of sonoluminescence produced by a single, stable, pulsating gas bubble indicate that the spectrum can be modeled by that for a blackbody at a temperature of nearly 40 000 K [R. Hiller, S. J. Putterman, and B. P. Barber, ''Spectrum of synchronous picosecond sonoluminescence,'' Phys. Rev. Lett. 69, 1182 (1992) ]. These results are in contrast with earlier measurements of the spectrum which is modeled by electronic transitions of rotational and vibrational bands within specific elements of the host liquid [E. B. Flint and K. S. Suslick, ''The temperature of cavitation,'' Science 253, 1397 (1991)]. It is suggested that the single-bubble SL observed by Hiller et al is intrinsically different from the multiple-bubble SL observed by Flint and Suslick. In the former caw, symmetric bubble collapse leads to shock wave formation in the gas; in the latter case, asymmetric bubble collapse leads to liquid jets that penetrate the hot bubble interior and result principally in incandescence of the host liquid.