Temperature dependence of single-bubble sonoluminescence threshold in sulfuric acid: An experimental study

We experimentally investigated the temperature dependence of intensity of single-bubble sonoluminescence (SBSL) in 85 wt %. sulfuric acid. It was found that the intensity increases as temperature increases from 15 °C and 25 °C, confirming what has been predicted by A. Moshaii et al. [Phys. Rev. E 84, 046301 (2011)] theoretically. This behavior, however, is completely opposite to what has been observed for water. Above 25 °C, the behavior of intensity of SBSL in sulfuric acid is found to be independent of the liquid temperature. Moreover, it was observed that as the temperature increases, contribution to total intensity from the UV portion of the spectrum increases while contribution from the visible portion decreases, indicating higher bubble temperatures at higher liquid temperatures. Results of this experiment further indicate that the intensity threshold at each temperature is not determined by the shape or the positional stability conditions but by the driving pressure at which the transition from SBSL to multibubble sonoluminescence (MBSL) takes place.

Figure 1

Experimental setup.

Figure 2

Number of photons detected per second by the PMT for five different temperatures.

Figure 3

SBSL threshold (stable SBSL to MBSL) as a function of temperature. The threshold is measured in volts, as it is the driving voltage of the transducers attached to the flask.

Figure 4

SBSL spectra of 85 wt % sulfuric for 15 °C and 30 °C. Ar emission lines are most prominent in 15 °C. Nevertheless, Ar emission lines are observed at all five temperatures: 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C.

Figure 5

Normalized SBSL intensities in the intervals 200–400 nm (UV) and 400–800 nm (visible) as a function of temperature. Note that the total intensity of SBSL emission increases when temperature varies from 15 °C to 25 °C and remains constant above 25 °C.