On the emitters of sulfuric acid sonoluminescence

Abstract

A comparative study of the sonoluminescence spectra of water and argon saturated aque ous H 2 SO 4 solutions was carried out. At an H 2 SO 4 concentration of 18 mol L -1 , the sulfuric acid sonoluminescence is fifty times more intense than water sonoluminescence. The sulfuric acid luminescence spectrum differs from the water sonoluminescence spectrum caused by the emission of excited water molecules and OH radicals from the gas phase of cavitation bubbles. The sulfuric acid sonoluminescence spectrum exhibits maxima at 330, 420, 500, and 630 nm. Emitters of sonoluminescence of sulfuric acid are the singlet (330-340 nm) and triplet (∼420 nm) excited SO 2 molecules formed by sonolysis of H 2 SO 4 molecules. Another product of sonolysis of H 2 SO 4 , atomic oxygen, is assumed to be responsible for the luminescence at λ = 630 nm.The mechanism of ultrasonic cavitation in liquids has been studied for about a century. Meanwhile, the essence of high energy processes occurring in cavitation bubbles (CBs), which are responsible for sonoluminescence and sonochemical reactions, are still to be clarified. 1 Studies of sonoluminescence of aqueous solutions of various com pounds including inorganic acids in comparison with the corresponding data for water are expected to clarify the mechanism of sonoluminescence, to find ways of en hancement of sonoluminescence intensity, and to dis close fields of application of this phenomenon.The effect of ultrasonic cavitation on aqueous solu tions of inorganic acids has been studied. 2-6 In argon saturated H 2 SO 4 solutions (at acid concentrations exceed ing 9 mol L -1 ) the H 2 SO 4 molecules decompose into sul fur, SO 2 , and H 2 S. 2 It was assumed 3 that breakdown of H 2 SO 4 molecules is due to energy transfer from the ex cited species produced in CBs to the H 2 SO 4 molecules and HSO 4 -ions on the CB walls. In concentrated solu tions, the H 2 SO 4 molecules present within CBs can also evaporate and interact with electrons produced 2 in the gas phase on elecrical breakdown of CBs. No sonolumine scence of sulfuric acid has been studied by the authors of Ref. 2. Sonolysis of hydrochloric and phosphoric acids was also investigated 3,4 without studying sonolumine scence.A sonoluminescence study 5 of argon saturated aque ous nitric acid solutions revealed a selective quenching of the 310 nm band of • OH radicals in the sonoluminescence spectrum on an increase in the HNO 3 concentration in the range 0-0.9 mol L -1 and an increase in the intensity of an H 2 O* luminescence band near λ = 275 nm. Further increase in the HNO 3 concentration leads to a decrease in the intensity of sonoluminescence throughout the entire spectrum.Thus, only a few studies on sonoluminescence of aque ous solutions of inorganic acids are available. At the same time, information on sonoluminescence of aqueous solu tions of strong electrolytes could clarify a "dispute" be tween the thermal and electric theories of sonolumine scence. According to the former theory, quasi adiabatic compression of a CB leads to heating o...

Sonoluminescence and dynamics of cavitation bubble populations in sulfuric acid

“…Due to their high emission power, noble gas bubbles in acids are ideal candidates for sonoluminescence studies, and the literature on such experiments is continuously growing. For SL in H 2 SO 4 , see for instance [8,9,10,11,12,13,14,15,16,18,17,19,20,21,22,23,24,25,26,27]. The basic mechanism of light emission in the acids is believed to be similar to that observed in other liquids like water (see e.g.…”

The influence of the temperature of a liquid on multibubble sonoluminescence of Tb3+ ions in an aqueous solution

“…In addition to metal atom sonoluminescence effects mentioned above, the MBSL of Ln 3+ ions (Ln = Ce, Eu, Tb, Gd, Dy) in aqueous solutions of LnCl 3 was recently observed [9][10][11]. A hypothesis of the excitation of Ln 3+ was suggested.…”

“…Indeed, such reemission completely explains glow of Ce 3+ , whose luminescence was caused by d-f transitions [9,12]. However, glow in the sonolysis of ions emitting light in intrashell f-f transi tions (Eu 3+ , Tb 3+ , Gd 3+ , and Dy 3+ ) cannot be explained by SPL [9][10][11][12]. In addition, intrabubble excitation of these ions was also substantiated by the isotope effect (an increase in the intensity of lan thanide luminescence caused by solvent deuteration), which was observed for MBSL in solutions of TbCl 3 [13,14].…”

“…Conversely, the luminescence of metal atoms in aqueous solutions of nonvolatile alkali halide salts has attracted much interest [4][5][6][7]. The mechanism of their interaction with bubbles is still the focus of attention of researchers concerned with sonochemical processes [8].In addition to metal atom sonoluminescence effects mentioned above, the MBSL of Ln 3+ ions (Ln = Ce, Eu, Tb, Gd, Dy) in aqueous solutions of LnCl 3 was recently observed [9][10][11]. A hypothesis of the excitation of Ln 3+ was suggested.…”

“…2), the intensity of which depends on the concentration of LnCl 3 and increases as the density and viscosity of solutions grow. It also depends on temperature [9,10]. Since Gd 3+ does not have radiation transitions in the region of Tb 3+ PL, gadolinium chloride (gadolinium is an element closest in its atomic weight to terbium) is most suitable for Abstract-The influence of temperature on the yield of multibubble sonoluminescence of Tb 3+ ions in an aqueous solution of TbCl 3 was studied over the temperature range 5-55°C.…”