Time-Correlated Photon Counting for Estimating the Duration of Na-Line and Continuum Emission Flashes in the Spectra of Multi-Bubble Sonoluminescence

The time-correlated photon counting technique using software is used to estimate the duration and succession of Na-line and continuum emission flashes upon irradiation of aqueous solutions of NaCl and Na dodecyl sulfate with ultrasound at a frequency of 20 kHz. The duration of Na flashes was determined as 5.1, 8.0, and 11.7 ns for 5 M NaCl, 0.5 M NaCl, and 5 mM Na dodecyl sulfate solutions, respectively. The duration of a continuum emission flash varied insignificantly within 2.1-2.9 ns for all solutions. The close correlation revealed between the Na-line and continuum emission flashes allows us to conclude that bubbles producing both types of flashes emit them simultaneously with a measured delay of similar to 0.5 ns for Na.