Time-Resolved Spectra of Sonoluminescence

Hiller, Robert A.; Putterman, Seth; Weninger, Keith

doi:10.1103/physrevlett.80.1090

Cited by 181 publications

(150 citation statements)

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“…2͑b͔͒ reflects the characteristic asymmetry of the dynamics, i.e., the fall time of the emitted radiance is longer than the rise time. 40 The ''black'' bubble's pulse width, however, is well outside the range of experimental observations [39][40][41][42] -with Ϸ500 ps it is too long. While shorter pulses can be obtained with smaller driving pressures and radii, e.g., Ϸ275 ps FWHM with P a ϭ1.2 atm and R 0 ϭ3.0 m, the average pulse widths are clearly overestimated in the blackbody model.…”

Section: B Calculating the Properties Of The Pulsesmentioning

confidence: 92%

“…In several experiments these pulse widths have been measured with filters of bandwidth ⌬ Ϸ100 nm 39 and ⌬ Ϸ40 nm, 42 or alternatively with a spectrographic procedure. 41 While Gompf et al 39 and Hiller et al 41 could not detect any spectral variation of the pulse width, a small increase toward the red wavelengths is reported by Moran and Sweider. 42 Within the present formalism, it is easy to integrate the spectral radiance over suitable wavelength intervals and to compare with the experimental results.…”

Section: B Calculating the Properties Of The Pulsesmentioning

confidence: 95%

“…A small difference like this, amounting to Ϸ16 ps here ͑at very different absolute intensities͒, can hardly be detected in today's experiments. [40][41][42] Moran and Sweider 42 do find longer pulses in the red, but only for lower water temperatures, where the bubbles can be driven at larger P a and R 0 ͑cf. Ref.…”

Section: Light Pulses and Spectra In The Refined Modelmentioning

confidence: 99%

“…The most simple explanation, namely, thermal blackbody radiation, has been discarded on two accounts: ͑i͒ blackbody radiation would be coupled to the dynamics of the temperature in the bubble, i.e., it is expected to change on the time scales of bubble dynamics, which from theoretical calculations seem to be longer than the observed pulse widths. [39][40][41][42] ͑ii͒ Gompf et al, 39,40 and later Hiller et al, 41 experimentally found the pulse width to be independent of the wavelength of the radiation. Moran and Sweider 42 find only a rather weak dependence in some parameter regimes.…”

Section: B the Merits Of The Bubble Dynamical Approachmentioning

confidence: 99%

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Sonoluminescence light emission

1999

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Single bubble sonoluminescence is not an exotic phenomenon but can quantitatively be accounted for by applying a few well-known, simple concepts: the Rayleigh-Plesset dynamics of the bubble's radius, polytropic uniform heating of the gas inside the bubble during collapse, the dissociation of molecular gases, and thermal radiation of the remaining hot noble gas, where its finite opacity ͑transparency for its own radiation͒ is essential. A system of equations based on these ingredients correctly describes the widths, shapes, intensities, and spectra of the emitted light pulses, all as a function of the experimentally adjustable parameters, namely, driving pressure, driving frequency, water temperature, and the concentration and type of the dissolved gas. The theory predicts that the pulse width of strongly forced xenon bubbles should show a wavelength dependence, in contrast to argon bubbles.

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Section: B Calculating the Properties Of The Pulsesmentioning

confidence: 92%

Section: B Calculating the Properties Of The Pulsesmentioning

confidence: 95%

Section: Light Pulses and Spectra In The Refined Modelmentioning

confidence: 99%

Section: B the Merits Of The Bubble Dynamical Approachmentioning

confidence: 99%

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Sonoluminescence light emission

1999

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“…Most experiments and theories indicate that the temperatures (or equivalent energy densities) inside the bubble can reach at least several 10 4 K and the short (80-300 ps [5,6]) light pulses consist of up to 10 7 photons in the visible range [2]. The question now arises if the experimental parameters can be altered such that these figures can be pushed to even more extreme values, i.e., can SBSL be upscaled?…”

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confidence: 99%

Predictions for Upscaling Sonoluminescence

Hilgenfeldt

Lohse

1999

Phys. Rev. Lett.

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Only a small fraction of the high-dimensional parameter space that governs the occurrence of stable single-bubble sonoluminescence (SBSL) has been explored so far. We predict that decreasing the acoustic driving frequency f upscales SBSL. More specifically, at f 5 kHz we expect more than 100 times as many photons per flash as at f 20 kHz and a flash width of about 1000 ps. The application of lower frequencies has to be assisted by reducing the partial inert gas pressure of the dissolved gas (e.g., stronger degassing) to maintain diffusive stability of the bubbles.[ S0031-9007(98) Experimentally [2] it was found that an efficient way to achieve more intense light is to cool the water. Decreasing the water temperature from 33 to 2.5 ± C gives nearly 1000 times more photons per pulse. Following the hydrodynamical/chemical approach to SBSL [7][8][9][10], the water temperature dependence was quantitatively accounted for by considering the temperature dependence of the material constants of water [11].In this paper we focus on the upscaling of SBSL by reducing the driving frequency f, a procedure suggested by Apfel [12]. The effect of reducing the frequency is twofold: (i) In the SL regime the dynamics of the bubble radius R͑t͒ is characterized by a long and relatively slow expansion that occurs during the negative pressure phase of the driving, and by a subsequent violent collapse. Because a smaller frequency gives the bubble more time to expand, it leads to a larger expansion ratio R max ͞R 0 (maximum radius divided by ambient radius) and a stronger collapse. Indeed, the example of Fig. 1 shows that, in comparison to frequencies commonly used today in experiment (e.g., f ഠ 20 40 kHz), more violent collapses can be reached (at fixed R 0 ) with smaller f. (ii) For smaller f the threshold of shape instability which limits the SBSL regime [8] is shifted towards larger bubbles which potentially emit more sonoluminescence light. Indeed, experiments with smaller f by Barber and Putterman [13] and by Cordry [14] found brighter SL bubbles. But what is the maximum light intensity which can be expected, and how should one choose the forcing pressure P a and the gas concentration in the liquid to achieve an optimal photon yield? The present study will make quantitative predictions for answers to these questions.Our analysis of upscaled SBSL is based on the hydrodynamical approach to SBSL [7][8][9][10], augmented by an approximate description of the thermal bremsstrahlung of the partially ionized gas inside the bubble [15,16].The bubble is driven by the harmonic driving P͑t͒ 2P a cos 2pft; it responds according to the RayleighPlesset (RP) dynamics [2,8,17,18]. The pressure p͑ ͑ ͑R͑t͒͒ ͒ ͒ inside the bubble is approximated by a spatially homogeneous van der Waals pressure. This approximation is well 1͞f. While in all cases, R 0 4 mm and P a 1.2 atm are the same, the maximum radius R max reached for 5 kHz is almost 7 times larger than for 50 kHz, leading to a more violent collapse. This is demonstrated in the inset which shows ho...

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