ON RECTIFIED DIFFUSION AND SONOLUMINESCENCE

If acoustically driven, a gas-filled bubble may exist indefinitely eve n in an unsaturated liquid through a process known as ''rectified diff usion.'' When the oscillation period is small compared with the gaseou s diffusion time, the radius of the steadily oscillating bubble can be determined by asymptotic methods, in the way pioneered by Eller and F lynn (1965). The next term in their expansion is evaluated here and is shown to be significant if the radius of the bubble is small or if th e amplitude of its oscillations is large. For the identical level of s aturation and the same conditions of excitation, multiple solutions ar e possible. As a result of resonance between overtones of the frequenc y of free bubble oscillation with the frequency of the acoustic drive, there generally exist, in addition to a stable large-radius, stable s mall-radius states. The relevance of the present results to sonolumine scence is briefly discussed.