Two components of Na emission in sonoluminescence spectrum from surfactant aqueous solutions |
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| Institution: | 1. Department of Physical Chemistry, Faculty of Chemical Engineering, University of Chemistry and Technology, Technická 5, 166 28 Prague 6, Czech Republic;2. Institute of Chemical Process Fundamentals of the Czech Academy of Sciences, Rozvojová 135, 165 02 Prague 6, Czech Republic;3. Institute of Macromolecular Chemistry, Heyrovského náměstí 2, 162 06 Prague 6, Czech Republic;4. Department of Polymers, Faculty of Chemical Technology, University of Chemistry and Technology, Technická 5, 166 28 Prague 6, Czech Republic;5. Department of Chemistry and Natural Compounds, Faculty of Food and Biochemical Technology, University of Chemistry and Technology, Technická 5, 166 28 Prague 6, Czech Republic;1. Institute of Fluid Mechanics and Heat Transfer, Vienna University of Technology, Resselgasse 3, 1040 Wien, Austria;2. Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Rozvojová 135, 165 02 Praha, Czech Republic;1. Institute of Chemical Process Fundamentals of the CAS, v. v. i., Prague, Czech Republic;2. School of Occupational Safety and Health, Chung Shan Medical University, Taichung, Taiwan, ROC;3. Department of Occupational Medicine, Chung Shan Medical University Hospital, Taichung 402, Taiwan, ROC |
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| Abstract: | Sonoluminescence from sodium dodecyl sulfate (SDS) aqueous solutions exhibits Na emission. The spectrum of Na emission was measured as a function of sonication time for a total of 30 min at an ultrasonic frequency of 148 kHz. The spectral line profiles changed with the sonication time, suggesting that the Na emission consists of two components: broadened lines, which are shifted from the original D lines, and unshifted narrow lines. The intensity of the unshifted narrow lines decreased at a greater rate than that of the broadened lines with increasing sonication time. This effect was enhanced at a higher acoustic power. The shifted broadened lines remained after sonication for 30 min. We propose that these quenching effects are caused by the accumulation of gases decomposed from SDS molecules inside bubbles. The CO2 gas dependence of Na emission in NaCl aqueous solutions showed a similar change in the line profiles to that in SDS aqueous solutions, which supported this proposition. The unshifted narrow lines are easily affected by foreign gases. The results suggest that the two components originate from different environments around the emitting species, although both of them originate from the gas phase inside bubbles. The generation mechanisms of the two components are discussed. |
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| Keywords: | Sonoluminescence Acoustic cavitation Na emission Sodium dodecyl sulfate NaCl |
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