Sonoluminescence of Bubbles Collapsing near Surfaces

• Applicant: Dr. Darya Radziuk
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2011 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 196140727

Interaction of ultrasound with a medium generates a unique type of reaction conditions. This is defined by short pulses of energy and large pressures. These physical consequences result from acoustic cavitation, which requires formation, growth and collapse of bubbles in a liquid. The rapid compression of a gas/vapour mixture in the bubble interior yields extremely hot spots (thousands K) with flashes of light (sonoluminescence) locally in an otherwise cold medium. The actual acoustic pressure felt by each bubble is not uniform because the spatial distribution and the range of bubble dynamics are broad. The result is a great variety in the number of photons per bubble collapse and different conditions of bubble interior. Moreover, the overall number of bubbles composing the cavitation cloud and those undergoing implosive collapse (i.e., the number of hot spots) at any given time are only qualitatively known. The main idea of my proposal is to use sonoluminescence to probe the physico-chemical conditions (temperature and pressure) of the bubble interior in the clouds near solid surfaces. I intend to study the spatial and temporal temperature distribution over groups of bubbles with different shape deformations and collapses close to solid surfaces. The aim of my study is to characterize processes inside the collapsing bubbles (reactions of molecular or atomic species and plasma conditions) and quantify hot spots. Experimentally, my goal is to treat solid surfaces ultrasonically under conditions of the most intense sonoluminescence and estimate the effective temperatures (pressures, energies) from the multi-bubble sonoluminescence emission spectra. I intend to compare the temperature profiles with those from previous sonoluminescence studies in bulk liquid as well as in case of single isolated bubbles. In terms of my project, I also plan to estimate the energy input to the solids by examination of the dramatic damages of the surface morphology. In summary in this

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Kenneth S. Suslick