Multibubble sonoluminescence pulses from Na atoms in viscous liquid

Area of Science:

• Acoustic cavitation
• Sonochemistry
• Spectroscopy

Background:

• Multibubble sonoluminescence (MBSL) is a phenomenon involving light emission from collapsing bubbles.
• Previous studies on MBSL pulse widths have yielded a wide range of values.
• Understanding bubble dynamics in viscous liquids is crucial for sonochemistry applications.

Purpose of the Study:

• To measure and characterize multibubble sonoluminescence pulses from a sodium (Na) and continuum emission in a viscous NaCl-ethylene glycol solution saturated with Xenon (Xe).
• To determine the intrinsic pulse width of Na emission and compare it with previous findings.
• To investigate the bubble dynamics associated with MBSL in viscous media.

Main Methods:

• Experiments were conducted using a 28 kHz acoustic cavitation setup.
• Multibubble sonoluminescence spectra, including Na and continuum emissions, were recorded.
• High-speed shadowgraphy was employed to observe bubble dynamics.
• High-speed movies (32000 frames per second) captured the sonoluminescence events.

Main Results:

• Na emission was observed to consist of both multiple-peak and single pulses.
• The intrinsic pulse width estimated from single pulses was 0.37 ns, significantly shorter than the 10-165 ns reported previously.
• Observations suggest multiple-peak pulses arise from the superposition of single peaks from fragmented bubbles undergoing repeated fragmentation and coalescence.

Conclusions:

• The observed short intrinsic pulse width and the fragmentation-coalescence mechanism indicate a unique MBSL behavior in viscous liquids.
• This phenomenon may be specific to the properties of viscous solutions like the NaCl-ethylene glycol mixture.
• Further research is needed to fully elucidate the dynamics of acoustic cavitation in complex fluids.