Sensitivity of sonoluminescence to experimental parameters

Abstract

Light-scattering measurements have enabled us to determine that the transition to sonoluminescence is characterized by a bifurcation in the dynamics of a trapped pulsating bubble. These experiments also reveal that in the sonoluminescence (SL) state, changes in bubble radius of only 20% are associated with factors of 200 in the intensity of emitted light. This sensitivity of SL suggests that it originates from the kind of singular behavior that arises from the implosion of a shock wave. Theoretical extrapolations of this model to energy scales for fusion are discussed.PACS numbers: 78.60. Mq, 42.65.Re, 43.25.+y, 47.40.Nm The radiation pressure of a resonant sound field in a liquid can trap a small gas bubble at a velocity node [1].At a sufltciently high sound intensity the pulsations of the bubble are large enough to prevent its contents from dissolving in the surrounding liquid [2,3]. For an air bubble in water, a still further increase in intensity causes these pulsations to become so enormous and nonlinear that the supersonic [4] inward collapse of the bubble concentrates the acoustic energy by over 12 orders of magnitude [5] so as to emit picosecond flashes [6] of broadband light which extend well into the ultraviolet [7] and which furthermore are synchronous [8] with the sound field to picosecond accuracy.We now use light scattering techniques to determine the dependence of the light emitting mechanism on the bubble dynamics. In particular we find that the transition to sonoluminescence (SL) involves a sudden decrease in the bubble's size. In the SL state changes in experimental parameters which vary the bubble radius by 20% cause a hundredfold increase in light emission. Measurements of the bubble's dynamic susceptibility suggest that while the parameter spacer for SL is sharply delineated, the establishment of a steady state involves long time scales on the order of seconds. Our calculations suggest that this extremely sensitive dependence of sonoluminescence on bubble dynamics originates from the singularity which forms when a shock wave implodes [9]. Idealized theoretical extrapolations indicate that as the shock radius passes through 60 A the temperatures and densities are high enough for fusion.The extreme sensitivity of SL to external parameters such as the water temperature and the sound field amplitude, is indicated in Fig. 1 which shows that, as the water temperature decreases from 40 C to 1 C, the intensity of the light emission increases by a factor of over 200.

Heat-induced formation of nitrogen oxides in water

“…The triggering of the collapse of nanobubbles may result from a local electromagnetic perturbation induced by the transition of oxygen into a singlet state [20]. It is known that the temperature and pressure inside a collapsing bubble are sufficient to overcome the energy threshold (E a = 941.4 kJ/mol) of the break of triple bonds in the nitrogen molecule [44].…”

Sonoluminescence light emission

“…17 The dependence of viscosity, gas solubility, and water vapor pressure on water temperature conspire to allow for larger maximal SBSL light intensities at lower water temperatures. 16,38 Further studies 17,37 elucidated the possibilities for achieving SL in larger bubbles or with more violent collapses ͑''upscaling''͒.…”

Nuclear Fusion in Collapsing Bubbles—Is It There? An Attempt to Repeat the Observation of Nuclear Emissions from Sonoluminescence

“…The spectrum of the emitted light indicates that the surface of the emitting bubble may be hotter than the surface of the sun [4]. It has been proposed [5] that the interior of the bubble may be hot and dense enough to facilitate thermonuclear fusion. In a recent paper Taleyarkhan et al [6] reported the possible observation of d-d fusion events occurring in collapsing bubbles formed by cavitation in deuterated acetone.…”