Abstract:

A novel method utilizing abrupt drive pressure amplitude changes is described for exploring the dynamics of single-bubble sonoluminescence. Air bubbles that are initially below the luminescence threshold are subject to an abrupt increase in the drive pressure amplitude. The resulting turn-on time for light emission is qualitatively similar to nitrogen bubbles, except that over time scales of seconds, the light intensity of an air bubble increases [B. P. Barber et al., ``Sensitivity of sonoluminescence to experimental parameters,'' Phys. Rev. Lett. 72, 1380 (1994)], while the intensity from a nitrogen bubble remains low. However, when we begin with a stable sonoluminescing air bubble above the luminescence threshold, and then generate an abrupt decrease in the pressure amplitude below the threshold (no light regime), followed again by an abrupt increase back to its original (sonoluminescing) state, the resulting turn-on time for light emission appears qualitatively similar to noble gas bubbles: sudden, and relatively intense, unlike what occurs for air bubbles that were initially below the luminescence threshold. These measurements imply that sonoluminescence from an air bubble depends on the time the bubble spends in the sonoluminescing state. [Research supported by NSF.]