Observation of Multibubble Sonoluminescence from Water Saturated with Various Gases during Ultrasonic Atomization

Multibubble sonoluminescence (MBSL) from water saturated with various atmospheric gases was observed using an ultrasonic atomizer (2.4 MHz). The majority of sonoluminescence (SL) in the system did not originate from capillary waves but from acoustic cavitation. The dependence of MBSL intensity on the type of dissolved gas was confirmed. Atomization occurred similarly in all cases. The intensities for the dissolved gases were in the following order: Ar > Air > O 2 > N 2 ≫He, H 2 , CO 2 . The intensity for water saturated with air is higher than those for the O 2 - and N 2 -saturated solutions. To examine the effect of gas mixing, MBSL was measured for various ratios of O 2 to N 2 . The maximum intensity was obtained at 40% O 2 /60% N 2 . In the regions above and below this ratio, the intensity decreased gradually. To explain this result, the possibilities of Ar rectification and chemical reactions between O 2 and N 2 gases were also discussed. After examination, it could not be confirmed that Ar rectification occurred. Chemical reactions of O 2 with N 2 proceed inside the cavitation bubble.