THE EFFECTS OF A SOLUBLE SURFACTANT ON QUADRUPOLE SHAPE OSCILLATIONS AND DISSOLUTION OF AIR BUBBLES IN WATER

Single air bubbles were ultrasonically trapped in aqueous solutions of the soluble surfactant Triton X-100. Quadrupole shape oscillations we re induced by modulation of the radiation pressure and the free decay was recorded using an optical extinction technique. The frequency and damping were found to be maximal al a bulk surfactant concentration wh ich only weakly affects the surface tension. At higher concentrations the frequency is reduced due to surface tension depression and the dam ping approaches a value several times that expected for a clean interf ace. These results are in qualitative agreement with theoretical predi ctions based on interfacial viscoelastic considerations, Bubble size a nd dissolution cui?ies were obtained through the use of digitized bubb le images. Dissolution rates are shown to be significantly enhanced by the presence of the surfactant. (C) 1997 Acoustical Society of Americ an. [S0001-4966(97)02712-4].