Sonoluminescence generated by the interaction of two ultrasonic fields with strongly different frequencies

The phenomenon of luminescence under the action of ultrasound (sonoluminescence, SL) was studied in a liquid exposed to the field of a high-frequency (HF, 880 kHz) focusing radiator with simultaneous or preliminary action of a low-frequency (LF, 19.9 kHz) ultrasound on the sample. It is shown that a nonadditive increase in the SL intensity takes place for simultaneously operating radiators and is observed for a long time (up to several hours) after switching off the LF source. This is evidence of a long-term aftereffect of the LF ultrasound on the magnitude of SL induced by the HF oscillations. The possible mechanisms of the observed effect are discussed.