Single-bubble sonoluminescence at two adjacent antinodes in a standing wave acoustic field.

This study employed both experimental observations and numerical simulations to investigate the formation mechanism of single-bubble sonoluminescence (SBSL) light pulses at two adjacent antinodes within a rectangular acoustic resonator. We recorded the light pulses emitted by SBSL at each antinode alongside the corresponding temporal evolution of the acoustic pressure. We calculated and simulated the temporal evolution of the bubble wall, number density of various internal particles, and radiated light pulses and spectra by integrating fluid dynamics equations, the Keller-Miksis equation, and spectroscopic theory. The results showed that the light pulse amplitude emitted by the bubble at the antinode with higher driving acoustic pressure was higher, which concurred with the experimental observations. This suggests that local acoustic pressure significantly influences sonoluminescence characteristics. In addition, the trends in the physical quantities, e.g., temperature, pressure, ionization degree, and energy spectrum, inside the bubbles at both antinodes matched those observed in SBSL within spherical acoustic fields, which underscores the theoretical and experimental importance of clarifying the sonoluminescence radiation mechanism. These findings will enable the optimization of sonochemical reactor designs and spatial control of acoustic cavitation processes in industrial applications.