This thesis will explore and study rhodium, a group VIII element that has rarely been studied.

M.Sc. / Please refer to full text to view abstract

Thesis advisor: Willie J. Padilla / Realization of an ideal electromagnetic absorber has long been a goal of engineers and is highly desired for frequencies above the microwave regime. On the other hand, the desire to control the blackbody radiation has long been a research topic of interest for scientists--one particular theme being the construction of a selective emitter whose thermal radiation is much narrower than that of a blackbody at the same temperature. In this talk, I will present the computational and experimental work that was used to demonstrate infrared metamaterial absorbers and selective thermal emitters. Based on these work, we further demonstrate an electrically tunable infrared metamaterial absorber in the mid-infrared wavelength range. A voltage potential applied between the metallic portion of metamaterial array and the bottom ground plane layer permits adjustment of the distance between them thus altering the electromagnetic response from the array. Our device experimentally demonstrates absorption tunability of 46.2% at two operational wavelengths. Parts of this thesis are based on unpublished and published articles by me in collaboration with others. The dissertation author is the primary researcher and author in these publications. The text of chapter two, chapter five, and chapter seven is, in part, a reprint of manuscript being prepared for publication. The text of chapter three is, in part, a reprint of material as it appears in Physical review letters 104 (20), 207403. The text of chapter four is, in part, a reprint of material as it appears in Physical Review Letters 107 (4), 45901. The text of chapter six is, in part, a reprint of material as it appears in Applied Physics Letters 96, 011906 / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Physics. / Includes bibliographical references. / M.S.

One of the most fundamental probes of the physics that underpins galaxy evolution is the star formation rate (SFR) as a function of cosmic time. In addition, the statistical prop- erties of galaxy populations are another important key to understand how the universe has been evolving. It is known that the far-infrared emission from galaxies is strongly correlated with obscured star formation and forms a significant part of cosmic infrared background. We thus investigate the variation of the SFR of galaxies over time by com- paring predictions of the L-Galaxies semi-analytic model with observations of the far infrared (FIR) luminosity and number counts. In the first part of this thesis, we follow the star formation histories (SFHs) of galaxies and use these to construct stellar spectra in post-processing. We then contrast model SFHs from the Millennium Simulation with observed ones from the VESPA algorithm as applied to the SDSS-7 catalogue when this has been characterized by mass and colour of galaxies. In order to investigate the SAM model prediction, I extend L-galaxies to predict far infrared fluxes and construct mock catalogues which are fed into SMAP in order to provide simulated maps. LFs have also been estimated for model galaxies at different redshifts. The results are compared with observations from Herschel. To conclude, our model under- estimates the number density of galaxies at bright sources (e.g fluxes above 0.02 Jy) also does not produce high luminosity objects especially at higher redshifts (e.g z > 1) . We show that by fitting the simulated IR luminosity function to observed LIR, our model is able to produce more bright sources at high redshifts and match reasonably well to the observed number counts.

本論文旨在利用高分辨激光光譜研究中紅外以及近紅外波段的分子體系。首先在固態氫體系中，我們主要研究其分別位於4 μm 及1.5 μm 的純轉動和振動轉動的W 躍遷（ΔJ=6）。我們搭建了一套全新的差頻激光光譜儀用以研究純轉動的W1(0)躍遷（ΔJ=6）；另外振動轉動W₀(0)躍遷（Δv=1，ΔJ=6）則是用到自行搭建的近紅外二極管激光光譜儀。由於激光光譜的分辨率極高，兩種W 躍遷都觀察到晶體場效應導致的三重分裂結構，我們基於定態激子模型還得到了相應的晶體場常數。另外，我們還研究了兩種W 躍遷的線型、頻率與溫度的關係（溫度在3.8 K 至11.8 K 區間），并基於德拜兩能級弛豫模型對此做出解釋，相信主要是由於晶體內聲子散射所引致的。 / 另外我們還研究了三種含過渡金屬元素的氣態雙原子分子，分別是RuC、IrP和IrB。通過聯用激光消融及超聲射流技術，我們研究這些分子體系在近紅外波段的激光誘導熒光光譜。對於RuC 分子，我們記錄了12000 至14000 cm⁻¹ 波段的電子光譜，包擴[附圖]和[附圖]這四個譜帶系統，并分析得到了所有七種同位素分子的各項分子常數。由於極高的分辨率，我們觀察到99RuC 和101RuC 這兩個同位素分子的超精細結構，并得到了它們的[附圖] 這三個電子態的超精細常數。對於IrP 分子，我們在12000 至14000 cm⁻¹ 波段發現了新的電子態躍遷，并得到¹⁹³IrP 和¹⁹¹IrP 這兩種同位素分子的分子常數。對於IrB 分子，我們指認了一個新的電子態躍遷³Δ₃-X³Δ₃，并得到了¹⁹¹Ir¹¹B and ¹⁹³Ir¹¹B 這兩種同位素分子的分子常數。 / This thesis reports the high resolution laser spectroscopic studies of molecular systems in the mid‐ and near‐ infrared regions. In the system of solid parahydrogen, spectrum in the pure rotational and rovibrational W (ΔJ=6) transitions in the 4 μm and 1.5 μm regions respectively have been studied. A high resolution difference frequency laser spectrometer was constructed from scratch for the study of the pure rotational W₀(0) (ΔJ=6) transition, while the rovibrational W₁(0) (Δv=1, ΔJ=6) transition was studied using a home‐built near infrared diode laser spectrometer. The exceedingly high resolution achieved by laser spectroscopy resolved the triplet structure for both transitions due to anisotropic crystal field interactions. Their corresponding crystal field parameters based on the model of localized exciton were determined. In addition, the temperature dependences of line profiles and transition frequencies in the range of 3.8‐11.8 K were also studied for both transitions. These observations were consistent with the Debye’s model for the dephasing of two‐level system by acoustic phonons in the bulk crystal. / Coupled with laser ablation and free jet expansion, high resolution laser induced fluorescence spectroscopy in the near infrared region was applied in the study of three transition metal containing diatomic molecules including RuC, IrP and IrB in the gas phase. For RuC molecule, rotational resolved electronic spectrum have been observed in the range of 12000‐14060 cm⁻¹, covering the [with formula], and the [with formula] band systems. The resolution of our spectrum allowed partially resolved hyperfine structure for both ⁹⁹RuC and ¹°¹RuC isotopes. Accurate molecular constants for all seven RuC isotopic molecules were obtained and hyperfine constants for the [with formula] and states of both ⁹⁹RuC and ¹°¹RuC isotopes were retrieved and analyzed. For IrP molecule, new electronic transition systems were observed in the range of 12000‐14000 cm⁻¹ and the molecular constants for both ¹⁹³IrP and ¹⁹¹IrP isotopes were obtained. For IrB molecule, a new ³Δ₃-X³Δ₃ transition system was identified with the molecular constants of two isotopes ¹⁹¹Ir¹¹B and ¹⁹¹Ir¹¹B derived. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Yang, Mei. / Thesis (Ph.D.) Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 82-85). / Abstracts also in Chinese.

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A series of seven functionalized near-infrared aza-BODIPY dyes have been synthesized and their spectroscopic properties measured. Their fluorescence emissions could be tuned by altering the electronic substituents on the aryl-groups. A through-bond energy transfer cassette featuring two fluorescein units as donor, and an aza-BODIPY dye as acceptor, was then synthesized and its preliminary spectroscopic properties examined. This cassette exhibited absorption and fluorescence characteristics that were highly dependent on the pH and the solvent polarity. Furthermore, no energy transfer was observed upon excitation of the donor. Novel near-infrared aza-BODIPY were also synthesized via a one-pot, two step reaction. Upon demethylation and intermolecular cyclization onto the B-atom, a ~ 100 nm red¬shift of both the absorption and fluorescence emission maxima could be observed. Through-bond energy transfer cassettes based on squaraines have also been synthesized and their spectroscopic properties studied. These cassettes exhibited fast and efficient energy transfer from the donor to the acceptor. In depth experiments have also been realized to correlate the rate of energy transfer and structure on 3 different sets of through-bond energy transfer cassettes. No correlations could be made between the rate of the energy transfer and the nature of the acceptor, and the distance between the donor and acceptor. Finally, the use of DPP (diketo-pyrrolopyrolle) pigment as a potential donor for through-bond energy transfer cassettes was investigated. Three water-soluble DPPs dyes were prepared and studied. They all displayed weak fluorescence in water.

Over recent decades, much has been learned about the perceptual capacity that enables infants to recognize and understand language. However, not until very recently have the neural mechanisms that are the substance of language learning been investigated. A recently developed optical imaging technique called near-infrared spectroscopy (NIRS) shows promise for being an acceptable alternative to invasive imaging techniques. NIRS measures correlates of neural activity by assessing hemoglobin concentration changes in the infant brain. The research presented here investigates neural activation in the left temporal and occipital cortex regions during exposure to speech and visual stimuli. As hypothesized, hemodynamic reaction was observed in both areas. Results indicate a significant activation in response to speech in the left temporal region, and an intriguing difference between uni- and bi-modally presented speech stimuli. These results have interesting implications for future multimodal studies of infant speech perception.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 207-215).