OH/D A2sigma(+)-X2pi(i) rovibronic transitions in multibubble sonoluminescence.

Multibubble sonoluminescence spectra were recorded in the 300-350 nm wavelength range in the case of H(2)O/Ar, D(2)O/Ar and H(2)O/Kr solutions (acoustic frequency: 20 kHz; spectral resolution optimized to 0.34 nm). Three groups of rotational components (R(1)/R(2), Q(1)/Q(2) and P(1)/P(2)) were identified in the OH/D A2sigma(+)-X2pi(i) (0,0) transitions via the substitution of H(2)O for D(2)O. The congestion of bands and the origin of a red shading extending up to 350 nm are broached.

Evidence for the emission of 'alkali-metal-noble-gas' van der Waals molecules from cavitation bubbles.

Visible emission spectra in the vicinity of resonance lines of alkali metals were recorded from acoustically cavitating aqueous and 1-octanol solutions (acoustic frequency: 20 kHz; solutes: Ar (or Kr), NaCl, RbCl or rubidium 1-octanolate). The maximum intrabubble density deduced from line shift data was approximately 5 +/- 0.7 x 10(26) m-3, i.e. approximately 18 +/- 2 amagats. It is demonstrated that (i) the emission from alkali metals arose from the gas phase of bubbles, (ii) the blue satellite and line distortions were induced, respectively, by B2 sigma+ - X2 sigma+ and A2II - X2 sigma+ transitions of 'alkali-metal/rare-gas' van der Waals molecules and (iii) excitation/de-excitation mechanisms are chemiluminescent in essence.

Experimental study of the liquid flow near a single sonoluminescent bubble

Tracers (sulphur particles produced in situ by a bubble itself, fuchsin spots and dust) were used to probe the liquid flows in the neighborhood of single sonoluminescent bubbles maintained in levitation in a resonant acoustic setup. The flows caused by the bubble were distinguished clearly from the streamings (mean Lagrangian velocity: approximately 20 microm/s) associated with resonant cells in the absence of a bubble. The liquid flow due to the presence of the bubble formed around it over a few mm. The radial component of the Lagrangian velocities (maximum value measured: approximately 260 microm/s) of this flow evolved as r(-1) , with r as the distance from the bubble, while the tangential component remained approximately constant (approximately 20 microm/s). In the Appendix by M. S. Longuet-Higgins, a simplified model of microstreaming involving a spherical bubble in translational and radial oscillation gives a qualitative description of the experiments. A fairly good agreement was observed between the experiments and the modeling, which involved a dipole flow enclosed in a Stokeslet.