Time-correlated single-photon counting reveals that the width of flash
es of sonoluminescence ranges from under 40 to over 350 ps for mixture
s of various gases in water. Flash widths and emission times are indep
endent of wavelength from the ultraviolet to the infrared. These measu
rements suggest that sonoluminescence originates in a plasma which que
nches as its temperature drops below the ionization potential. For hel
ium bubbles this model implies peak temperatures greater than or simil
ar to 20 eV. [S0031-9007(97)05155-7].