Sonoluminescence

Ultrasonics Sonochemistry, 2012

The influence on luminescence from conical bubble collapse (CBL) with varying Ar gas content while perturbing the liquid 1,2-Propanediol (PD) has been investigated. The temporal, spatial, and spectral features were analysed with regards to the dynamics of collapse and liquid degradation. Sulphuric acid and sodium chloride were added to disturb the liquid. The following three cases were studied: PD/Ar, (I), (PD + H 2 SO 4 )/Ar, (II), and (PD + H 2 SO 4 + NaCl)/Ar, (III). The intensities of those cases decrease as III > II > I. Temporally, single and multiple light emissions were found to occur. The pulse shape exhibited a large variety of profiles with a main maximum and up to two local maxima around the main maximum. These local maxima resembled those generated by laser cavitation. Spatially, no radial symmetry was detected in the light emissions. Spectrally, the Swan, CH and CN lines were observed at low volumes of gas and driving pressure. The Å OH radical and OH-Ar bands, as well as the Na and K lines, consistently appeared superimposed on an underlying continuum that almost disappeared in (III). The Na line was observed with two satellite diffuse bands representing Na-Ar complexes in (I) and (II), whereas in (III), only the line of sodium could be seen. Weak and diffuse emission lines from the Ar atom in the near-IR region were observed in (I) and (II).

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.

Ultrasonics Sonochemistry, 2012

Micromachined pits on a substrate can be used to nucleate and stabilize microbubbles in a liquid exposed to an ultrasonic field. Under suitable conditions, the collapse of these bubbles can result in light emission (sonoluminescence, SL). Hydroxyl radicals (OH . ) generated during bubble collapse can react with luminol to produce light (sonochemiluminescence, SCL). SL and SCL intensities were recorded for several regimes related to the pressure amplitude (low and high acoustic power levels) at a given ultrasonic frequency (200 kHz) for pure water, and aqueous luminol and propanol solutions. Various arrangements of pits were studied, with the number of pits ranging from no pits (comparable to a classic ultrasound reactor), to three-pits. Where there was more than one pit present, in the high pressure regime the ejected microbubbles combined into linear (two-pits) or triangular (three-pits) bubble clouds (streamers). In all situations where a pit was present on the substrate, the SL was intensified and increased with the number of pits at both low and high power levels. For imaging SL emitting regions, Argon (Ar) saturated water was used under similar conditions. SL emission from aqueous propanol solution (50 mM) provided evidence of transient bubble cavitation. Solutions containing 0.1 mM luminol were also used to demonstrate the radical production by attaining the SCL emission regions. † Email address for correspondence: [email protected] arXiv:1208.0669v1 [physics.chem-ph]

Ultrasonics, 2010

The strong dependence of the intensity of single bubble sonoluminescence (SBSL) on water temperature observed in experiment can be accounted for by the temperature dependence of the material constants of water, most essentially of the viscosity, of the argon solubility in water, and of the vapor pressure. The strong increase of light emission at low water temperatures is due to the possibility of applying higher driving pressures, caused by increased bubble stability. The presented calculations combine the Rayleigh-Plesset equation based hydrodynamical/chemical approach to SBSL and full gas dynamical calculations of the bubble's interior.

Angewandte Chemie International Edition, 2010

When a liquid is subjected to high-intensity ultrasound, bubbles are formed, grow, and implosively collapse. This phenomenon of acoustic cavitation generates both chemical reactions (i.e., sonochemistry) and the emission of light (i.e., sonoluminescence, SL). It is generally agreed that both sonochemistry and sonoluminescence result from the intense compressional heating of gas and vapor inside the collapsing bubbles, and the extraordinary temperatures and pressures thus created. The emission of light can occur either from a cloud of cavitating bubbles (i.e., multibubble sonoluminescence, MBSL), or in a carefully controlled standing wave acoustic field from a single isolated bubble (i.e., single-bubble sonoluminescence, SBSL). MBSL is more closely related to sonochemistry, and quantification of the conditions generated during MBSL can lead to a better understanding of sonochemistry. Measurement of atomic and molecular emission from volatile species during MBSL revealed effective temperatures of thousands of Kelvins created during bubble collapse. Little is known, however, about the origin of emission derived from nonvolatile species during MBSL. This emission is directly relevant to the observed sonochemistry of dissolved reactants.

Chinese Physics B, 2011

Based on a quasi-adiabatic model, the parameters of the bubble interior for a moving single bubble sonoluminescence (m-SBSL) in water are calculated. By using a complete form of the hydrodynamic force, a unique circular path for the m-SBSL in water is obtained. The effect of the ambient pressure variation on the bubble trajectory is also investigated. It is concluded that as the ambient pressure increases, the bubble moves along a circular path with a larger radius and all bubble parameters, such as gas pressure, interior temperature and light intensity, increase. A comparison is made between the parameters of the moving bubble in water and those in N-methylformamide. With fluid viscosity increasing, the circular path changes into an elliptic form and the light intensity increases.

Physical Review E, 2005

The properties of the luminescence pulse from collapsing laser-created bubbles in pressurized water are studied for pressures between 0.25 and 15 bars. The duration of the light pulse is found to be linear in the maximum bubble size, but for a given bubble size it increases with the applied pressure p as p 0.38. The number of photons emitted increases quadratically with the bubble size, and increases approximately linearly with pressure. The spectrum of the luminescence is blackbody in form, with a temperature that increases somewhat with pressure, from 8100 K at 1 bar to 9400 K at 10 bars. At higher pressures the blackbody temperature drops, but this is primarily due to the rapid onset above 10 bars of a fission instability, where the bubbles split into two just before the collapse point.

The Journal of Physical Chemistry A, 2011

Spectroscopic studies of single-bubble sonoluminescence (SBSL) in water and aqueous sodium chloride solutions with a defined concentration of argon were performed as a function of the driving acoustic pressure. The broad-band continuum ranging from 200 to 700 nm is characterized by fits using Planck's law of blackbody radiation. The obtained blackbody temperatures are in the range of 10 4 K and are revealed to be independent of the presence of a salt and the acoustic pressure, whereas the SL intensity increases by a factor of more than 10 within the studied acoustic pressure range. The different trends followed by SL intensity and blackbody temperatures question the blackbody model. In solutions with 70 mbar of argon, line emissions of OH • radicals and Na* are observed. The shape of the OH • radical emission spectrum is very similar to that in MBSL spectra, indicating the strong similarity of intrabubble conditions. An increase of the acoustic pressure causes the continuum to overlap the lines until they become indistinguishable. The emission line of Na* in NaCl is observed only at high NaCl concentrations. When sodium dodecylsulfate is used a pronounced Na* line is already observed in a 1 mM solution thanks to enrichment of sodium ions at the interface. The results presented in this work reveal the strong similarity of SBSL and MBSL under certain experimental conditions.