Brown, Dennis E.
Esen E. Alp
Ph.D. (Doctor of Philosophy)
Department of Physics
Nuclear resonance time domain interferometry (NR-TDI) is used to study the slow dy- namics of liquids (that do not require M ̈ossbauer isotopes) at atomic and molecular length scales between 1 A to 10 nm and at time scales between 1 ns to 10 μs. This new spectroscopy technique covers a new range of previously unexplored momentum transfers between 1 to 100 nm−1 and energies between 10 peV to 100 neV allowing an investigation into the dynami- cal motion of molecules, liquids, and glasses. The notoriously low count rate from quasielastic scattering experiments makes measurements difficult when using synchrotron x-rays or ra- dioactive sources. The introduction of an annular slit allowed the entire diffraction ring to be measured, instead of only a fraction of the ring, increasing the count rate by two orders of magnitude at the peak of the structure factor of glycerol. The fabrication of the annular slits increased the count rate sufficiently that it allowed for measurements at different momentum transfers with low scattering intensities. These measurements can give new insights into the dynamics of the liquids improving the understanding about their behavior under different conditions of temperature, pressure, and length scales. The intermediate scattering function describes the motion of molecules in liquids under different temperatures and momentum transfers using the Kohlrausch–Williams–Watts (KWW) stretch exponential as a model. The relaxation times from the KWW model gives insight into the dynamics of the electron density fluctuations of glycerol. I was able to measure relaxation times from 5 to 70 000 ns. The Vogel–Fulcher–Tammann (VFT) equation was used to determine the glass transition ?Tg = 185 K? of glycerol, and the Arrhenius equation was used to find its activation energy (Ea = 63 kJ mol−1). With the addition of an annular slit, NR-TDI experiments can be easily implemented at any beamline using a single detector, eliminating the need multiple detec- tors. The increase in count rate using an annular slit makes it possible to do material science experiments on various liquid systems like glycerol, liquid crystals, proteins, colloids, and biomolecules.
Pavlik, Marc, "Study of the Dynamics of Glasses Using Nuclear Resonance Time Domain interferometry" (2023). Graduate Research Theses & Dissertations. 7173.
Northern Illinois University
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