9500653 Williams This project is devoted to the study of cryogenic fluids. The major project is interdisciplinary and involves aspects of physics, chemistry and optical science. The research deals with the new phenomena of sonoluminescence; particularly single bubble sonoluminescence. A vapor bubble, trapped at the center of fluid contained in an acoustic resonator, radiates bright flashes of light that are easily seen by the naked eye. In the process, energy densities can increase by a factor of 1012, and 50- picosecond light pulses are synchronized with the acoustic cycle to a few parts in 1011. This project extends the sonoluminescence experiments to low temperatures by employing cryogenic fluids (nitrogen, argon, neon, and helium). Initial experiments with nitrogen have revealed a spectacular increase in luminosity over prior room temperature work involving aqueous media. The mechanism of the sonoluminescence in not known, and this project will obtain information that may allow a mechanism and theory of the sonoluminescence to be developed. Additional subprojects deal with helium films adsorbed in porous materials, sound propagation in these fluids, and a theoretical study of the nature of the superfluid transition in helium. %%% This project is devoted to the study of cryogenic fluids. The major project is interdisciplinary and involves aspects of physics, chemistry and optical science. The research deals with the new phenomena of sonoluminescence; particularly single bubble sonoluminescence. A vapor bubble, trapped at the center of fluid contained in an acoustic resonator, radiates bright flashes of light that are easily seen by the naked eye. This project extends the sonoluminescence experiments to low temperatures by employing cryogenic fluids (nitrogen, argon, neon, and helium). Initial experiments with nitrogen have revealed a spectacular increase in luminosity over prior room temperature work involving aqueous media. The mechanism of the sonoluminescence in not known, and this project will obtain information that may allow a mechanism and theory of the sonoluminescence to be developed. Additional subprojects deal with helium films adsorbed in porous materials, sound propagation in these fluids, and a theoretical study of the nature of the superfluid transition in helium. ***
