Sonoluminescence from metal carbonyls

Spectrally resolved sonoluminescence is observed from the ultrasonic irradiation of organometallic compounds in silicone oil solutions. Specifically, ultrasonic irradiation of solutions of Fe(CO)₅, Cr(CO)₆, Mo(CO)₆, and W(CO)₆ produces atomic line emission from metal atom excited states. The intensity of this sonoluminescence is the highest yet observed. Sonoluminescence arises from acoustic cavitation (the formation, growth, and implosive collapse of bubbles), which produces localized hot spots with extreme temperatures and pressures and very short lifetimes. The mechanism proposed for this observed sonoluminescence invokes the extreme temperatures created during acoustic cavitation to strip carbon monoxide from the metal complexes and to thermally populate electronic excited states of the metal atoms.