Thesis (M.S. in chemical engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 21, 2010). "Department of Chemical Engineering." Includes bibliographical references (p. 28-31).

Graduation date: 1995

Graduation date: 1992

Selective excitation pulsed NMRON, CW-NMRON and Thermal NMR methods have been used to study the low temperature ⁵⁴Mn nuclear spin-lattice relaxation mechanisms in magnetic insulators. The selective single and double quantum excitation sequences have been used for the first time in NMRON to obtain single and double quantum rotation patterns, Free Induction Decays, Hahn spin echoes and pulsed T₁ measurements. Two insulating magnets have been studied; MnCl₂.4H₂O and Mn(COOCH₃ )₂ .4H₂O. In the ⁵⁴Mn-MnCl₂ .4H₂O system the temperature dependence of the ⁵⁴Mn spin-lattice relaxation time at zero field was measured between 35 mK and 90 mK and it was found that the dominant relaxation process between 65 mK and 90 mK is an electronic magnon Raman process and below 65 mK a direct relaxation process dominates. Single and double quantum Free Induction Decays and Hahn spin echoes have been used to determine the magnitude and nature of the spin-spin relaxation mechanism for ⁵⁴Mn oriented in MnCl₂.4H₂O at zero applied field. NMRON was observed for the first time in the paramagnetic phase of MnCl₂.4H₂O. The resonance lines are inhomogeneously broadened and 300 kHz wide. A value of <⁵⁴AS>/h=-513.6(3) MHz has been determined for the paramagnetic phase hyperfine coupling constant, and this value has been used to determine the zero point spin deviation of the antiferromagnetic phase. The field and temperature dependence of the ⁵⁴Mn T₁ was measured for values of field above the spin flop paramagnetic phase transition and a field dependent T₁ minimum was discovered at Ba=2.64 T. For the ⁵⁴Mn-Mn(COOCH₃) .4H₂O system two ⁵⁴Mn resonances have been observed and the value of the hyper fine coupling constants for the two sites were found to be <⁵⁴AS>/h=-435 (1) MHz for the ⁵⁴Mn1 site and <⁵⁴AS>/h=-478(1) MHz for the ⁵⁴Mn2 site. The high field spin-lattice relaxation behavior has also been investigated and a T₁ minimum at Ba =2.74 T analogous to that observed in MnCl₂ .4H₂O was discovered. A Hahn echo study of the low field single quantum spin-spin relaxation processes has been performed and anomalous behavior of the spin echo amplitude revealed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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This work examines the use of higher order multiphoton resonances in higher harmonic generation together with judicious exploitation of coherent interaction properties to achieve efficient harmonic generation. A detailed experimental study on third harmonic generation in two photon resonant coherent interaction and a theoretical study on four photon resonant coherent interaction have been conducted. Two photon resonant coheren propagation in lithium vapor (2S-4S and 2S-3D interaction) has been studied in detail as a function of phase and delay of the interacting pulse sequence. Under coherent lossless propagation of 90 phase shifted pulse pair, third harmonic generation is enhanced. A maximum energy conversion efficiency of 1% was measured experimentally. This experiment shows that phase correlated pulse sequence can be used to control multiphoton coherent resonant effects. A larger two photon resonant enhancement does not result in more efficient harmonic generation, in agreement with the theoretical prediction. An accurate (to at least 0.5 A°) measurement of intensity dependent Stark shift has been done with the newly developed "interferometric wavemeter." Stark shifts as big as several pulse bandwidths (of picosecond pulses) result in a poor tuning of multiphoton resonance and become a limiting factor of resonant harmonic generation. A complete theory has been developed for harmonic generation in a four photon resonant coherent interaction. A numerical application of the theory to the Hg atom successfully interprets the experimental observations in terms of the phase dependent stimulated Raman scattering. With the intensity required for four photon resonant transition, the calculation predicts a dramatic Stark shift effect which completely destroys the resonance condition. This model provides a basis for the development of future schemes for efficient higher order coherent upconversion.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 118-123). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 118-123). Also available on the Internet.

Thesis (doctoral)--Lund University, 1998. / Thesis statement inserted. Includes bibliographical references.

Thesis (doctoral)--Lund University, 1998. / Thesis statement inserted. Includes bibliographical references.