In order to observe laser phase noise, this noise must be converted to amplitude noise, which can be achieved using either an interferometer or an absorption resonance in an atomic/molecular vapor or gas. When phase noise is converted to amplitude noise, it is manifested as a heterodyne signal in the output of an optical square-law detector. Thus, phase noise is measured by optical heterodyne spectroscopy, or, equivalently, laser phase noise spectroscopy. In recent work on diode laser noise spectroscopy of rubidium and oxygen, the observed spectroscopic lineshapes were not in total agreement with theoretical predictions. We have repeated the previous work on the oxygen A-band transitions, and we now find qualitative agreement with theory. In addition, we have measured the diode laser noise spectrum of a Lummer- Gehrcke interferometer (LGI), comparing the heterodyne lineshape of a LGI transmission spectrum with a qualitative theory that we develop in this thesis. A theory, from other workers, predicts the intensity fluctuations from a Doppler-broadened, two-level atomic/molecular system driven with a phase-diffusing laser field. We show that a simplified version of this theory, which ignores Doppler effects of the system, is a useful approximation to the complete theory, by comparing computer-generated heterodyne lineshapes of each, for a rubidium transition. We apply this approximate theory to an oxygen A-band transition, and compare these results with our experimental measurements. For the experimental arrangement used in the present work, diode laser noise spectroscopy may also include effects of selective reflection, which is dealt with experimentally and theoretically. Diode laser phase noise has practical importance in optical communications and atomic clocks. / Graduation date: 1999

The electronegativities of -SF���, -CF���SO���, and -SO���F have been measured with gas phase X-ray photoelectron spectroscopy. Of these three groups previously measured values were found only for -SF���. The electronegativities of -Cl, -Br, -CF���, and -CF���, were concurrently measured to determine how the findings of this research compare with other experimental values found in the literature. Our experimental electronegativities for -SF���, -CF���SO���, and -SO���F are 2.81 �� 0.12, 2.49 �� 0.09, and 2.92 �� 0.12 respectively. The electronegativity of -CF���, currently measured (2.78 �� 0.08) is significantly lower than other experimental values. The electronegativity of -SF��� is in agreement with other experimental values. The experimental electronegativities are compared with theoretical values calculated based on the assumption of Electronegativity Equalization and based on Mulliken's definition of electronegativity. It is found that the electronegativities calculated with Electronegativity Equalization are higher than the experimental values currently measured, and those calculated with Mulliken's definition are lower than the experimental values. / Graduation date: 1999

A procedure for evaluating the precision of atomic absorption measurements is presented and applied to 21 elements under varying instrumental conditions. The experimental relative standard deviations (RSD's) in absorbance obtained from repetitive measurements made with a high resolution voltmeter and on-line computer, are compared to those predicted by a recently proposed theoretical equation. Good agreement between theory and experiment is obtained which indicates the usefulness of the theoretical equation and evaluation procedure. The study reveals that, under the conditions used for atomic absorption measurements for the 21 elements, the noise associated with the lamp (i.e., signal shot noise and source flicker noise) and with the flame (i.e., flame transmission flicker noise) limit the precision at small absorbances (i.e., A < 0.1 ). Flame transmission flicker noise generally increases with the flame absorbance. Over most of the analytically useful range of absorbances (i.e., 0.1 > A > 1.0-1.5) analyte absorption flicker limits the precision to a value near 1% RSD for one second integration periods. The precision can be improved by a factor of two to three for any absorbance region with ten second integration periods, although not much better than this with any longer integration periods. Precision at high absorbances (i.e., A > 1.0-1.5) is limited by emission noises (analyte and background). For longer wavelengths, the analyte emission noises become more significant. The limiting noises' frequency dependence is obtained with noise power spectra and analyte absorption, emission, and fluorescence flicker are shown to all have a similar 1/f (inverse frequency) character, as well as a value of about 1% for the RSD for Cu. Abbreviated procedures for evaluation of noise in atomic emission (AE) and atomic fluorescence measurements are presented. Other studies into the source of analyte absorption noise are presented, and the conclusion is drawn that this flicker noise is probably due to nebulization fluctuations, non-fundamental in nature. The study of these various noise sources' dependence on the instrumental parameters (e.g. burner position, slit height and width, flame type and stoichiometry, and lamp current) suggest how to optimize conditions or concentrations so that an analysis can be carried out with maximum precision. / Graduation date: 1978

Graduation date: 1994

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 134-151). Also available in electronic version.

Thesis (M.S.)--Oregon Graduate Center, 1976.

Thesis (Ph. D.)--Oregon Graduate Center, 1979.

M.S. / Applied Physics / This monograph summarizes the theory and construction of a tunable continuous wave (CW) Rhodamine 6G dye laser longitudinally pumped by an argon laser. (from Introduction; no abstract available)

The function of biomolecules is very sensitive to structure. Folding in proteins and nucleic acids is a hierarchical process progressing from primary to secondary, then tertiary, and finally, quaternary structures. RNA in its folded form performs a variety of biological activities. Obtaining intramolecular distance measurements makes it possible to generate structural models along the folding pathway that may be related to the overall function of the molecule. Distances can be measured by Site-Directed Spin-Labeling (SDSL), in which nitroxyl spin-label probes are attached and observed by EPR spectroscopy. Spin-labels can provide information concerning structure and conformational changes because they are particularly sensitive to molecular motion and interspin distances. Continuous-wave EPR spectroscopy has been commonly applied to detect and monitor nitroxide spin-label probes within biological systems. A previous published SDSL study from this laboratory investigated a 10-mer RNA duplex model system with spin-label probe succinimdyl-2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-carboxylate; however, an increased spin-labeling efficiency was observed with an isocyanate derivative of tetramethylpiperidyl-N-oxy (TEMPO). In this thesis, a 4-isocyano TEMPO spin-label probe replaced the previously used succinimdyl-2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-carboxylate in 10-mer SDSL studies. The influence of labeling with the 4-iscocyano TEMPO spin-label in a 10-mer RNA model system was investigated with thermal denaturation, Matrix Assisted Laser Desorption Time of Flight Mass Spectrometry (MALDI-TOF-MS), Electron Paramagnetic Resonance (EPR) spectroscopy, and reverse phase high performance liquid chromatography (RP-HPLC). In the 10-mer RNA duplex model system a 4-isocyano TEMPO spin-label is individually attached to one strand and two strands are annealed to measure distances. This methodology is limited to systems in which two oligonucleotides are annealed together. To circumvent this limitation and also to explore single-strand dynamics a new methodology was implemented, double spin-labeling. Double spin-labeled single-stranded RNA was investigated as a single-strand and within a duplex via MALDI-TOF-MS, EPR spectroscopy and RP-HPLC. A double spin-labeling strategy in this work will be applicable to large complex RNAs like Group I intron of Tetrahymena thermophilia.

This research work focused on studying the emission spectroscopy produced from the high energy ion-molecule collision processes in mass spectrometry. The collision experiments are described and divided into 4 chapters (Chapter 3, 4, 5, 6).N2O+● is an ion of atmospheric importance. In chapter 3 the investigation of the collision between high translational energy (4-8 keV range) N2O+● ions and Helium target gas in mass spectrometry using collision induced emission (CIE) spectroscopy is described.In chapter 4, the collision-induced emission (CIE) spectra from 4-8 keV collisions between projectile He+● ions and CO2 target gas (He+●/CO2) were obtained. In Chapter 5, to probe the validity of this hypothesis, CIE experiments were carried out to observe the photon emissions from keV collisions of a selection of projectile ions with O2 target gas. By studying the resulting CIE spectra, a second potential mechanism came to light, one that involves the nearly isoenergetic O2+. A → X state transition. In chapter 6, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as recovery signals in neutralization-reionization mass spectrometry in the modified VG-ZAB mass spectrometer.