Li Yuen Yee Laura = 激光懸浮慢速揮發微液滴之彈性散射光之研究 / 李婉兒. / Thesis submitted in: August 2005. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 97-99). / Text in English; abstracts in English and Chinese. / Li Yuen Yee Laura = Ji guang xuan fu man su hui fa wei ye di zhi tan xing san she guang zhi yan jiu / Li Waner. / Acknowledgements --- p.3 / Abstract --- p.4 / Chapter Chapter 1 --- Introduction --- p.6 / Chapter Chapter 2 --- Theory --- p.10 / Chapter 2.1 --- "Cross sections for absorption, scattering and extinction" --- p.10 / Chapter 2.2 --- Morphology-dependent resonances and spherical cavity modes assignment --- p.11 / Chapter 2.3 --- Broadening of MDR and removal of degeneracy --- p.15 / Chapter 2.4 --- Radiation pressure and stable levitation position --- p.17 / Chapter 2.4.1 --- Radiation pressure --- p.17 / Chapter 2.4.2 --- Laser levitation --- p.19 / Chapter 2.4.3 --- Stable levitation positions --- p.23 / Chapter 2.5 --- T-matrix method --- p.25 / Chapter Chapter 3 --- Experiment --- p.30 / Chapter 3.1 --- Choice of liquid --- p.30 / Chapter 3.2 --- Simultaneous recording of the differential cross-section and the position of a laser-levitated dodecane microdroplet --- p.30 / Chapter 3.3 --- Dual-wavelength experiment --- p.35 / Chapter Chapter 4 --- Data Analysis --- p.37 / Chapter 4.1 --- Upper and lower limits on the size parameter --- p.38 / Chapter 4.2 --- Refractive index --- p.40 / Chapter 4.3 --- Evaporation rate --- p.42 / Chapter 4.4 --- Acceptance angle --- p.43 / Chapter 4.5 --- Vertical position --- p.44 / Chapter Chapter 5 --- Results and Disscussions --- p.53 / Chapter 5.1 --- High-order MDR's --- p.53 / Chapter 5.2 --- Signatures of low-order resonances --- p.64 / Chapter 5.3 --- Discussions --- p.69 / Chapter Chapter 6 --- Conclusion and Future Outlook --- p.90 / Appendix 1 --- p.92 / List of Figures --- p.94 / List of Tables --- p.96 / References --- p.97

This thesis concerns itself with the applicability of quantum field methods, in the fixed field approximation, to problems involving a weak gravitational field. After introducing general scattering relations, various classic problems are reviewed to illustrate various approaches to solving scattering problems. Newtonian and quantum mechanical field methods are illustrated using Coulomb scattering. Classical relativity is used to solve the bending of light rays by the sun. Finally, quantum field methods are used to solve the scattering of polarized photons by the sun. The additional problems of scattering of light by a mass distribution and by a rotating mass are calculable using this method. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In preparation for laser light scattering experiments on plasmas in magnetic fields a pulsed ruby laser has been developed in conjunction with a multichannel spectral analyser for detection of the scattered light. The laser, consisting of separate oscillator and amplifier rods has a spectral line width of .08 Å at powers up to 100 Megawatts. The use of a Pockels Cell as the Q-switch permits accurate synchronization with the spectral analyser and all external electronics. For the multichannel detection system five fiber optics slit bundles transmit light from the output of a monochromater to five photomultipiier tubes, which are gated on for 100 nsec during the laser pulse. The pulses are displayed sequentially to give an intensity vs. wavelength profile on an oscilloscope screen. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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The entire sixteen element scattering matrix for two parallel dielectric fibers over an angular range of θ = 5°-170° as measured from the forward θ = 0 direction has been experimentally measured using the polarization modulation technique. Experimental results were in good agreement with theory for light scattering from two parallel fibers. Measurements were made for both endside and broadside illuminations at normal incidence for fibers at various separations from 2 μm to 70 μm. Laser wavelengths used were 632.8 nm and 441.2 nm, and fiber radii were 0.400±0.002 μm, 0.370±0.002 μm, 0.428±0.002 μm, and 0.406±0.002 μm. Special care was taken to measure the fiber radii, fiber separation, and to establish the parallelism between the two fibers. Electrostatic attraction between the fibers prevented the investigation for separation below 2 μm. A vibration detection device based on two-fiber light scattering has also been suggested.

The amount of information (types of solutions, accuracy and moments of the solution) about tropospheric rural aerosol size distribution that can in theory be obtained from backscattered measurements, without using any additional information about the anticipated solution, has been discussed. In practice, additional assumptions (constraints) must be used to solve for aerosol size distribution. The inferred solution reflects those assumptions and is therefore not objective. The quality of the solution depends on the applicability of the constraints to the given problem. A library of pseudo-empirical functions is used to form a set of orthogonal basis functions. It is assumed that any unknown aerosol size distribution may be constructed from a linear sum of these basis functions. The problem then becomes one of solving for the unknown coefficients of the basis functions. A solution with a smoothing constraint and a positivity constraint has been developed. Results of the method, when backscattered radiation is used as measurements, are presented. Discussion on the limitations of the method and the effects upon the solution of the different assumptions that are used is given. Some possible uses of the solution are considered.

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