Line Emission of Sodium and Hydroxyl Radicals in Single-Bubble Sonoluminescence

Abstract

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.

Plasma Formation during Acoustic Cavitation: Toward a New Paradigm for Sonochemistry

“…• radical SBSL spectrum obtained in water preequilibrated with 70 mbar of Ar is very similar to that observed in MBSL spectra of argon-saturated water at 20 kHz, indicating the strong similarity of intrabubble conditions for SBSL and MBSL under certain experimental conditions [45].…”

Toward a new paradigm for sonochemistry: Short review on nonequilibrium plasma observations by means of MBSL spectroscopy in aqueous solutions

“…On the other hand, an increase in acoustic power in ranges usual for sonochemistry has no significant influence on vibronic temperatures but leads to an increase of total intensity of MBSL. Another interesting phenomenon described in the literature is that the shape of OH Å radical SBSL spectrum obtained in water pre-equilibrated with 70 mbar of Ar is very similar to that observed in MBSL spectra of argon-saturated water at 20 kHz, indicating the strong similarity of intrabubble vibronic temperatures for single bubble and multibubble cavitation under certain experimental conditions [52].…”

Turning single bubble sonoluminescence from blue in pure water to green by adding trace amount of carbon nanodots

“…The light emission from OH • usually has its maximum at 310 nm [12] , [41] . The emission peak from OH • at 280 nm and 340 nm can also be identified obviously in SL experiments by many groups [11] , [40] , [42] . In our experiment, the light emissions around 280 nm and 340 nm are much stronger than the emission around 310 nm which cannot be clearly identified in experimental spectrum, although the peak at 310 nm can be decomposed theoretically (see cyan dotted curve in lower panel of Fig.…”