Sonoluminescence Spectra Research Articles

Spectrum of synchronous picosecond sonoluminescence.

The clocklike emission of picosecond pulses of light with a peak power over 30 mW has been observed to originate from a bubble trapped at the velocity node of a resonant sound field in water. The spectrum of this bright sonoluminescence is broadband and our measurements show that if a spectral peak exists, it lies at photon energies above 6 eV.

Sonoluminescence spectra of water

Sonoluminescence spectra of water

The Temperature of Cavitation

Ultrasonic irradiation of liquids causes acoustic cavitation: the formation, growth, and implosive collapse of bubbles. Bubble collapse during cavitation generates transient hot spots responsible for high-energy chemistry and emission of light. Determination of the temperatures reached in a cavitating bubble has remained a difficult experimental problem. As a spectroscopic probe of the cavitation event, sonoluminescence provides a solution. Sonoluminescence spectra from silicone oil were reported and analyzed. The observed emission came from excited state C(2) (Swan band transitions, d(3)IIg-a(3)II(micro)), which has been modeled with synthetic spectra as a function of rotational and vibrational temperatures. From comparison of synthetic to observed spectra, the effective cavitation temperature was found to be 5075 +/- 156 K.

The effect of ultrasound power on water sonoluminescence

Sonoluminescence is observed from water saturated with argon and xenon for the 200–500 nm wavelength interval when these solutions are insonified at a frequency of 22 kHz. The total intensity of the light emission in the Xe-saturated water is stronger than in the Ar-saturated water. The spectrum of Xe-saturated water has a strong band near 260 nm. The sonoluminescence spectra does not change markedly with increasing ultrasound power. The sonoluminescence intensity of water in the presence of Xe increases over the whole range of ultrasound power used, but for Ar-saturated waters the sonoluminescence intensity stops increasing when the ultrasound power reaches the value of 9·2 W/cm 2. The explanation of the results obtained is in accordance with thermal theory, corresponding to the differences between the characteristics of argon and xenon.

The sonochemical hot spot

The origin of “sonochemistry” is acoustic cavitation: the formation, expansion, and implosive collapse of bubbles in liquids irradiated with ultrasound. The compression of such bubbles generates intense local heating, which has been quantified recently from both chemical kinetic thermometry and from high-resolution sonoluminescence spectra. The temperatures reached during cavitation are ≈5000 K, but have an effective lifetime of only a few microseconds. Consistent with this, the sonoluminescence that accompanies sonochemistry closely resembles flame emission! The chemistry generated by these hot spots is different than either ordinary thermal or photochemical processes and sonochemistry represents a fundamentally unique interaction of energy and matter. [For recent reviews see K. S. Suslick, Sci. Am. 260, 80 (Feb. 1989) and Science 247, 1439 (1990).] Recently, the use of ultrasound in liquid-powder slurries to enhance dramatically their chemical reactivity has been explored. For example, heterogeneous catalysis can be induced in normally nonreactive metals and the catalytic activity of Ni has been enhanced by 105. Using a variety of surface science techniques, it was shown that ultrasound removed the passivating oxide coating normally found on Ni and other metal surfaces, thus increasing their activity. The origin of these effects comes from extremely high-speed interparticle collisions which occur during ultrasonic irradiation of liquid-solid slurries. Turbulent flow and shockwaves produced by acoustic cavitation can drive metal particles together at sufficiently high velocities to induce melting upon collision. A series of transition metal powders have been used to probe the maximum temperatures and speeds reached during such interparticle collisions. Metal particles that are irradiated in hydrocarbon liquids with ultrasound undergo collisions at roughly half the speed of sound and generate localized effective temperatures between 2600°C and 3400°C at the point of impact. [Work supported by NSF and the UIUC Materials Res. Lab.]

Sonoluminescence from alkali-metal salt solutions

Sonoluminescence spectra from alkali-metal salt solutions in water and in primary alcohols are characterized by unusually broad resonance line emission from excited-state alkali-metal atoms. The spectral width and positions of sonoluminescence from potassium in primary alcohols are independent of both solvent vapor pressure and inert gas (Ar/He) ratio. Since the intensity of cavitational heating is dependent on both of these parameters, alkali-metal sonoluminescence cannot be used to determine the local conditions created by acoustic cavitation, contrary to earlier reports. In contrast, the intensity of this sonoluminescence is highly dependent on these two factors. This apparent paradox is explained if the excited-state alkali-metal atoms are the result of secondary reactions of metal ions with high-energy radicals formed directly in the cavitation event. The large line width is caused by rapid collisional deactivation of the excited-state atoms.

Sonoluminescence from nonaqueous liquids: emission from small molecules

Sonoluminescence spectra from nonaqueous liquids under a variety of gases are presented. Ultrasonic irradiation of alkanes under Ar leads to emission from C2, C2H, and CH. When nitrogen is present, emission is seen from CN. When oxygen is present, emission from COz, CH, and OH is observed. Ultrasonic irradiation of tetrachloroethylene or CCI4 leads to emission from CI2. The intensity of sonoluminescence decreases as the liquid vapor pressure increases. The properties of the dissolved gas also influence the sonoluminescence observed. Sonoluminescence is caused by chemical reactions of high energy species formed during cavitational collapse. It is a form of chemiluminescence. The principal source of sonoluminescence is not blackbody radiation or electrical discharge. Ultrasonic irradiation of liquids can produce light. This phenomenon, known as sonoluminescence (SL), was first observed from water in 1934 by Frenzel and Schultesl and from organic liquids in 1937 by Chambers.* Although sonoluminescence from aqueous solutions has been studied in some detai1,3,4 little work on sonoluminescence from nonaaueous liauids has been reDorted. and Leeman have recently proposed a shock-wave model? where SL is caused by a shock-wave from the collapsing bubble wall. In the hot-spot chemiluminescence m ~ d e l , ! ~ J ~ which is the best (1) Frenzel, H.; Schultes, H. 2. Phys. Chem. 1934, 276, 421. (2) Chambers. L. A. J . Chem. Phvs. 1937. 5. 290. We present here sonoluminescence spectra from several nonaqueous liquids in the presence of various gases. We conclude that sonoluminescence from organic liquids is caused by emission from small free radicals and molecules, such as C2, CN, C02, and Cl,. A preliminary reports of this work has been published. There has been some dispute over the mechanism of sonolumine~cence.~ All of the theories of SL invoke acoustic cavitation6 (the formation, growth, and implosive collapse of bubbles in solution), as the source of the phenomenon. Noltink and Neppiras proposed SL was from blackbody emission' of the heated cavity. Electrical discharge8 inside the bubble has been proposed several (3) Verrall, R. E.; Sehgal, C. M. Ultrasound: its Chemical, Physical, and Biological Effects; Suslick, K. S., Ed.; VCH Publishers: New York, 1988. (4) Walton, A. J.; Reynolds, G. T. Adu. Phys. 1984, 33, 595. (5) Suslick, K. S.; Flint, E. B. Nature (London) 1987, 330, 553. (6) (a) Atchley, A. A.; Crum, L. A. In Ultrasound its Chemical, Physical, and Biological Effects; Suslick, K. S. , Ed.; VCH Publishers: New York, 1988. (b) Neppiras, E. A. Phys. Rep. 1980, 61, 159. (7) Noltink, B. E.; Neppiras, E. A. Proc. Phys. SOC. 1950, 638 , 674. (8) (a) Harvey, E. N. J. Am. Chem. SOC. 1939,61,2392. (b) Frenkel, Ya. I . Russ. J . Phys. Chem. 1940, 14, 305. (c) Degrois, M.; Baldo, P. Ultrasonics 1974, 14, 25. (d) Margulis, M. A. Ultrasonics 1985, 23, 157. (9) Vaughan, P. W.; Leeman, S. Ultrason. Int . Con$ (Proc.) 1987, 297. (10) Fitzgerald, M. E.; Griffing, V.; Sullivan, J . J . Chem. Phys. 1956, 25, 976 times as the source of SL, most recently by M a r g ~ l i i . ~ ~ Vaughan (1 1 ) (a) Suslick, K. S.; Hammerton, D. A,; Cline, R. E. J. Am. Chem. SOC. 1986, 108, 5641. (b) Suslick, K. S.; Hammerton, D. A,; Cline, R. E. IEEE Trans. Ultrason., Ferroelectr., Freq Control 1986, UFFC-33, 143. (c) Suslick, K. S.; Cline, R. E.; Hammerton, D. A. IEEE Ultrason. Symp. 1985, 1 1 16. *Author to whom correspondence should be addressed. 0002-7863/89/ 15 11-6987$01.50/0

Sonoluminescence seen in nonaqueous liquids

Chemists at the University of Illinois, Urbana-Champaign, have obtained the first sonoluminescence spectra from hydrocarbon and halocarbon liquids. According to assistant professor Kenneth S. Susli...

Sonoluminescence from non-aqueous liquids.

Our understanding of the chemical effects of high-intensity ultrasonic irradiation of liquids is still quite limited. It is generally accepted that sonochemistry results from acoustic cavitation: the creation, growth, and implosive collapse of bubbles in ultrasonically irradiated liquids. The mechanism of sonoluminescence in aqueous systems has been a matter of some dispute; recent discussions have suggested at least three possible origins: black-body emission, chemiluminescence from radical recombination, and electric discharge. Few studies of non-aqueous sonoluminescence, however, have been conducted. We present here the first spectrally resolved sonoluminescence spectra from hydrocarbon and halocarbon liquids. These spectra originate unambiguously from excited-state molecules created during acoustic cavitation. These high-energy species probably result from the recombination of radical and atomic species generated during the high temperatures and pressures of cavitation.

Sonoluminescence

The results of our studies of sonoluminescence are summarized. Sonoluminescence spectra are interpreted in terms of the distribution of spectral intensity with wavelength, the spectral changes that occur due to scavenging of radiative species, and the shift and the broadening of emission bands. Estimates of conditions within a bubble during collapse are obtained from the spectral features. There is considerable evidence that sonoluminescence is produced by chemical processes induced by thermal mechanism.

Optical spectra of sonoluminescence from transient and stable cavitation in water saturated with various gases

Optical spectra of sonoluminescence from transient and stable cavitation in water saturated with various gases

Acoustic design of ultrasonic cleaners: Neppiras, E. A.Akust. Zh., 8, no. 1, p. 7 (1962)

Cavitation in agitated liquids has been discussed for over five decades as a phenomenon that could play a role in the appearance of structural changes in the solvent of potentised dilutions. However, its lack of specificity as well as the absence of experimental confirmation have so far confined the idea to theory. The light emission associated with cavitational bubble collapse can be used to detect and study cavitation in fluids. The phenomenon has been extensively studied when driven by ultrasound, where it is called sonoluminescence. Sonoluminescence spectra reflect extremely high temperature and pressure in the collapsing bubbles and are parameter sensitive. This article tries to examine whether, despite objections and difficulties, the detection or the study of cavitational luminescence in solutions during potentisation could be useful as a physical tool in high dilution research.