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Experiments On Tracer Diffusion In Aqueous And Non-Aqueous Solvent Combinations, Duncan M. Frasch, Daniel Spiegel
Experiments On Tracer Diffusion In Aqueous And Non-Aqueous Solvent Combinations, Duncan M. Frasch, Daniel Spiegel
Physics and Astronomy Faculty Research
Forced Rayleigh scattering is used to study the tracer diffusion of an azobenzene in binary combinations of polar solvents, including water. In the absence of water, the tracer diffusion coefficient D in the mixture lies between the diffusion coefficients within the pure solvents, on a curve that is reasonably close to the prediction of free-volume theory. If water is present, on the other hand, the diffusion coefficient displays a minimum that is less than the smaller of the two pure-solvent values. We attempt to understand the different behavior in water by concentrating on the fairly hydrophobic nature of the solute, …
Transient Diffraction Grating Measurements Of Molecular Diffusion In The Undergraduate Laboratory, Daniel Spiegel, Santona Tuli
Transient Diffraction Grating Measurements Of Molecular Diffusion In The Undergraduate Laboratory, Daniel Spiegel, Santona Tuli
Physics and Astronomy Faculty Research
Mass diffusion is a central process in many biological, chemical, and physical systems, and although the mathematics of diffusion has long been an important component of an undergraduate physics education, experimental measurements of diffusion are not very common in the undergraduate laboratory. We describe here an experiment that employs the interference of laser beams to allow measurement of molecular diffusion on micron length scales. The interference fringes of two intersecting “pump” beams within a dye solution create a sinusoidal distribution of long-lived molecular excited states. A third “probe” beam is incident at a wavelength at which the indices of refraction …