Effect of alcohols on the initial growth of multibubble sonoluminescence

The effect of alcohols on the initial growth of the multibubble sonoluminescence (MBSL) intensity in aqueous solutions has been investigated. With increasing concentrations of the alcohols, the number of pulses required to grow the MBSL intensity to a steady state (N-crit) increases (relative to that of water) initially to a maximum for all the alcohols used in this study, followed by a decrease for methanol and ethanol. The cause of the initial increase in N-crit is attributed to the inhibition of bubble coalescence in the system. This inhibition in bubble coalescence results in a population of bubbles with a smaller size range and thus a larger number of pulses is required to grow the bubbles to their sonoluminescing size range. It is suggested that the decrease in the N-crit at higher alcohol concentrations may be caused by an increase in the bubble growth by rectified diffusion.