Résumé
The use of acoustic cavitation to clean surfaces is known, as well as the influence of experimental parameters such as the nature of dissolved gas or of solutes on sonochemical activity, but the studied frequency range hardly goes beyond ≈ 1 MHz, because of power limitations. The UTINAM institute has developed a method to greatly increase or decrease the cavitation activity of a 4-MHz HIFU transducer (High Intensity Focused Ultrasound) by modulating the frequency of the exciting signal (vobulation). This process also makes it possible to control the location of acoustic cavitation.Vobulation can generate clouds of cavitation bubbles that are intensified compared to emission at a fixed frequency, as was quantified by measurements of SL intensity [1]. It is reported here that SL spectra can be recorded at frequencies as high as 4 MHz and that it is possible to identify and simulate different molecular emissions, such as OH (A-X), CN (B-X) and C2 Swan bands, and thus estimate their rovibronic temperatures[2] to see the influence of various transducer excitation parameters (power, frequency scanning rate, upper and lower scanning limits, etc.).This work is the result of a collaboration between two French institutes (ICSM in Marcoule and UTINAM in Besançon) with funding from the M2P Technology Institute for Research of Metz.[1] Hallez L. et al., Ultrason. Sonochem., 2016, 29, 194-197. [2] Ji R. et al., J. Phys. Chem. B, 2018, 122(27), 6989-6994.