Sonoluminescence spectra were collected from $\mathrm{Cr}(\mathrm{CO}{)}_6$ solutions in octanol and dodecane saturated with various noble gases. The emission from excited-state metal atoms serves as an internal thermometer of cavitation. The intensity and temperature of sonoluminescence increases from He to Xe. The intensity of the underlying continuum, however, grows faster with increasing temperature than the line emission. Dissociation of solvent molecules within the bubble consumes a significant fraction of the energy generated by the collapsing bubble, which can limit the final temperature inside the bubble.

• Received 12 July 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.777