1. Astronomical photometry at wavelengths of 8.5, 10.5, and 11.6 µm. 2. Infrared emission from asteroids at wavelengths of 8.5, 10.5, and 11.6 µm

The purpose of this thesis is to present new observations of thermal-infrared radiation from asteroids. Stellar photometry was performed to provide standards for comparison with the asteroid data. The details of the photometry and the data reduction are discussed in Part 1. A system of standard stars is derived for wavelengths of 8.5, 10.5 and 11.6 µm and a new calibration is adopted. Sources of error are evaluated and comparisons are made with the data of other observers.

The observations and analysis of the thermal-emission observations of asteroids are presented in Part 2. Thermal-emission lightcurve and phase effect data are considered. Special color diagrams are introduced to display the observational data. These diagrams are free of any model-dependent assumptions and show that asteroids differ in their surface properties.

On the basis of photometric models, (4) Vesta is thought to have a bolometric Bond albedo of about 0.1, an emissivity greater than 0.7 and a true radius that is close to the model value of 300^(+50)_(-30)km. Model albedos and model radii are given for asteroids 1, 2, 4, 5, 6, 7, 15, 19, 20, 27, 39, 44, 68, 80, 324 and 674. The asteroid (324) Bamberga is extremely dark with a model (~bolometric Bond) albedo in the 0.01 - 0.02 range, which is thought to be the lowest albedo yet measured for any solar-system body. The crucial question about such low-albedo asteroids is their number and the distribution of their orbits.

Deep near-infrared spectroscopy of high-redshift galaxies: the physical growth of passive systems

The assembly history of massive galaxies is one of the most important aspects of galaxy formation and evolution. Although we have a broad idea of what physical processes govern the early phases of galaxy evolution, there are still many open questions. In this thesis I demonstrate the crucial role that spectroscopy can play in a physical understanding of galaxy evolution. I present deep near-infrared spectroscopy for a sample of high-redshift galaxies, from which I derive important physical properties and their evolution with cosmic time. I take advantage of the recent arrival of efficient near-infrared detectors to target the rest-frame optical spectra of z > 1 galaxies, from which many physical quantities can be derived. After illustrating the applications of near-infrared deep spectroscopy with a study of star-forming galaxies, I focus on the evolution of massive quiescent systems.

Most of this thesis is based on two samples collected at the W. M. Keck Observatory that represent a significant step forward in the spectroscopic study of z > 1 quiescent galaxies. All previous spectroscopic samples at this redshift were either limited to a few objects, or much shallower in terms of depth. Our first sample is composed of 56 quiescent galaxies at 1 < z < 1.6 collected using the upgraded red arm of the Low Resolution Imaging Spectrometer (LRIS). The second consists of 24 deep spectra of 1.5 < z < 2.5 quiescent objects observed with the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE). Together, these spectra span the critical epoch 1 < z < 2.5, where most of the red sequence is formed, and where the sizes of quiescent systems are observed to increase significantly.

We measure stellar velocity dispersions and dynamical masses for the largest number of z > 1 quiescent galaxies to date. By assuming that the velocity dispersion of a massive galaxy does not change throughout its lifetime, as suggested by theoretical studies, we match galaxies in the local universe with their high-redshift progenitors. This allows us to derive the physical growth in mass and size experienced by individual systems, which represents a substantial advance over photometric inferences based on the overall galaxy population. We find a significant physical growth among quiescent galaxies over 0 < z < 2.5 and, by comparing the slope of growth in the mass-size plane dlogR_e/dlogM_∗ with the results of numerical simulations, we can constrain the physical process responsible for the evolution. Our results show that the slope of growth becomes steeper at higher redshifts, yet is broadly consistent with minor mergers being the main process by which individual objects evolve in mass and size.

By fitting stellar population models to the observed spectroscopy and photometry we derive reliable ages and other stellar population properties. We show that the addition of the spectroscopic data helps break the degeneracy between age and dust extinction, and yields significantly more robust results compared to fitting models to the photometry alone. We detect a clear relation between size and age, where larger galaxies are younger. Therefore, over time the average size of the quiescent population will increase because of the contribution of large galaxies recently arrived to the red sequence. This effect, called progenitor bias, is different from the physical size growth discussed above, but represents another contribution to the observed difference between the typical sizes of low- and high-redshift quiescent galaxies. By reconstructing the evolution of the red sequence starting at z ∼ 1.25 and using our stellar population histories to infer the past behavior to z ∼ 2, we demonstrate that progenitor bias accounts for only half of the observed growth of the population. The remaining size evolution must be due to physical growth of individual systems, in agreement with our dynamical study.

Finally, we use the stellar population properties to explore the earliest periods which led to the formation of massive quiescent galaxies. We find tentative evidence for two channels of star formation quenching, which suggests the existence of two independent physical mechanisms. We also detect a mass downsizing, where more massive galaxies form at higher redshift, and then evolve passively. By analyzing in depth the star formation history of the brightest object at z > 2 in our sample, we are able to put constraints on the quenching timescale and on the properties of its progenitor.

A consistent picture emerges from our analyses: massive galaxies form at very early epochs, are quenched on short timescales, and then evolve passively. The evolution is passive in the sense that no new stars are formed, but significant mass and size growth is achieved by accreting smaller, gas-poor systems. At the same time the population of quiescent galaxies grows in number due to the quenching of larger star-forming galaxies. This picture is in agreement with other observational studies, such as measurements of the merger rate and analyses of galaxy evolution at fixed number density.

Synthesis and spectroscopy of ruthenium-modified nucleic acids

Redox-active probes are designed and prepared for use in DNA-mediated electron transfer studies. These probes consist of ruthenium(II) complexes bound to nucleosides that possess metal-binding ligands. Low- and high-potential oxidants are synthesized from these modified nucleosides and display reversible one-electron electrochemical behavior. The ruthenium-modified nucleosides exhibit distinct charge-transfer transitions in the visible region that resemble those of appropriate model complexes. Resonance Raman and time-resolved emission spectroscopy are used to characterize the nature of these transitions.

The site-specific incorporation of these redox-active probes into oligonucleotides is explored using post-synthetic modification and solid-phase synthetic methods. The preparation of the metal-binding nucleosides, their incorporation into oligonucleotides, and characterization of the resulting oligonucleotides is described. Because the insertion of these probes into modified oligonucleotides using post-synthetic modification is unsuccessful, solid-phase synthetic methods are explored. These efforts lead to the first report of 3'-metallated oligonucleotides prepared completely by automated solid-phase synthesis. Preliminary efforts to prepare a bis-metallated oligonucleotide by automated synthesis are described.

The electrochemical, absorption, and emissive features of the ruthenium-modified oligonucleotides are unchanged from those of the precursor metallonucleoside. The absence of any change in these properties upon incorporation into oligonucleotides and subsequent hybridization suggests that the incorporated ruthenium(II) complex is a valuable probe for DNA-mediated electron transfer studies.

The photochemistry of dioxorhenium(V)

The excited-state properties of trans-ReO₂(py)₄⁺ (ReO₂⁺) in acetonitrile solution have been investigated. The excited-state absorption spectrum of ReO₂⁺ is dominated by bleaching of the ground state MLCT and d-d systems. The reduction potential of ReO₂^2+/+* is estimated from emission and electrochemical data to be -0.7 V (SSCE). The ReO₂⁺ excited state efficiently reduces methylviologen and other pyridinium and olefin acceptors. The resulting Re(VI) species oxidizes secondary alcohols and silanes. Acetophenone is the product of sec-phenethyl alcohol oxidation.

The emission properties of ReO₂⁺ in aqueous solutions of anionic and nonionic surfactants have been investigated. The emission and absorption maxima of ReO₂⁺ are dependent on the water content of its environment. Emission lifetimes vary over four orders of magnitude upon shifting from aqueous to nonaqueous environments. The emission lifetime has a large (8.6) isotope effect (k(H₂O)/k(D₂O)) that reflects its sensitivity towards the environment. These properties have been used to develop a model for the interactions of ReO₂⁺ with sodium dodecyl sulfate (SDS). A hydrophobic ReO₂⁺ derivative, ReO₂(3-Ph-py)₄⁺, has been used to probe micelles of nonionic surfactants, and these results are consistent with those obtained with SDS.

The emission properties of ReO₂⁺ in Nafion perfluorosulfonated membranes have been investigated. Absorption and emission spectroscopy indicate that the interior of the membrane is quite polar, similar to ethylene glycol. Two well-resolved emission components show different lifetimes and different isotope effects, indicative of varying degrees of solvent accessibility. These components are taken as evidence for chemically distinct regions in the polymer film, assigned as the interfacial region and the ion cluster region.

The unsubstituted pyridine complex shows monophasic, τ = 1.7 µs, emission decay when bound to calf thymus DNA. Switching to the 3-Ph-py complex yields a biphasic emission decay (τ₁ = 2.4 µs, τ₂ = 10 µs) indicative of an additional, solvent-inaccessible binding mode. Photoinduced electron transfer to methylviologen leads to oxidative cleavage of the DNA as detected by gel electrophoresis. Electrochemical and spectrophotometric techniques used with organic substrates also can be used to monitor the oxidation of DNA. Abstraction of the ribose 4' hydrogen by ReO₂²⁺ is a possible mechanism.

Chemical and mineralogical characterization of micro-inclusions in diamonds

Secondary-ion mass spectrometry (SIMS), electron probe analysis (EPMA), analytical scanning electron microscopy (SEM) and infrared (IR) spectroscopy were used to determine the chemical composition and the mineralogy of sub-micrometer inclusions in cubic diamonds and in overgrowths (coats) on octahedral diamonds from Zaire, Botswana, and some unknown localities.

The inclusions are sub-micrometer in size. The typical diameter encountered during transmission electron microscope (TEM) examination was 0.1-0.5 µm. The micro-inclusions are sub-rounded and their shape is crystallographically controlled by the diamond. Normally they are not associated with cracks or dislocations and appear to be well isolated within the diamond matrix. The number density of inclusions is highly variable on any scale and may reach 10^(11) inclusions/cm^3 in the most densely populated zones. The total concentration of metal oxides in the diamonds varies between 20 and 1270 ppm (by weight).

SIMS analysis yields the average composition of about 100 inclusions contained in the sputtered volume. Comparison of analyses of different volumes of an individual diamond show roughly uniform composition (typically ±10% relative). The variation among the average compositions of different diamonds is somewhat greater (typically ±30%). Nevertheless, all diamonds exhibit similar characteristics, being rich in water, carbonate, SiO_2, and K_2O, and depleted in MgO. The composition of micro-inclusions in most diamonds vary within the following ranges: SiO_2, 30-53%; K_2O, 12-30%; CaO, 8-19%; FeO, 6-11%; Al_2O_3, 3-6%; MgO, 2-6%; TiO_2, 2-4%; Na_2O, 1-5%; P_2O_5, 1-4%; and Cl, 1-3%. In addition, BaO, 1-4%; SrO, 0.7-1.5%; La_2O_3, 0.1-0.3%; Ce_2O_3, 0.3-0.5%; smaller amounts of other rare-earth elements (REE), as well as Mn, Th, and U were also detected by instrumental neutron activation analysis (INAA). Mg/(Fe+Mg), 0.40-0.62 is low compared with other mantle derived phases; K/ AI ratios of 2-7 are very high, and the chondrite-normalized Ce/Eu ratios of 10-21 are also high, indicating extremely fractionated REE patterns.

SEM analyses indicate that individual inclusions within a single diamond are roughly of similar composition. The average composition of individual inclusions as measured with the SEM is similar to that measured by SIMS. Compositional variations revealed by the SEM are larger than those detected by SIMS and indicate a small variability in the composition of individual inclusions. No compositions of individual inclusions were determined that might correspond to mono-mineralic inclusions.

IR spectra of inclusion- bearing zones exhibit characteristic absorption due to: (1) pure diamonds, (2) nitrogen and hydrogen in the diamond matrix; and (3) mineral phases in the micro-inclusions. Nitrogen concentrations of 500-1100 ppm, typical of the micro-inclusion-bearing zones, are higher than the average nitrogen content of diamonds. Only type IaA centers were detected by IR. A yellow coloration may indicate small concentration of type IB centers.

The absorption due to the micro-inclusions in all diamonds produces similar spectra and indicates the presence of hydrated sheet silicates (most likely, Fe-rich clay minerals), carbonates (most likely calcite), and apatite. Small quantities of molecular CO_2 are also present in most diamonds. Water is probably associated with the silicates but the possibility of its presence as a fluid phase cannot be excluded. Characteristic lines of olivine, pyroxene and garnet were not detected and these phases cannot be significant components of the inclusions. Preliminary quantification of the IR data suggests that water and carbonate account for, on average, 20-40 wt% of the micro-inclusions.

The composition and mineralogy of the micro-inclusions are completely different from those of the more common, larger inclusions of the peridotitic or eclogitic assemblages. Their bulk composition resembles that of potassic magmas, such as kimberlites and lamproites, but is enriched in H_2O, CO_3, K_2O, and incompatible elements, and depleted in MgO.

It is suggested that the composition of the micro-inclusions represents a volatile-rich fluid or a melt trapped by the diamond during its growth. The high content of K, Na, P, and incompatible elements suggests that the trapped material found in the micro-inclusions may represent an effective metasomatizing agent. It may also be possible that fluids of similar composition are responsible for the extreme enrichment of incompatible elements documented in garnet and pyroxene inclusions in diamonds.

The origin of the fluid trapped in the micro-inclusions is still uncertain. It may have been formed by incipient melting of a highly metasomatized mantle rocks. More likely, it is the result of fractional crystallization of a potassic parental magma at depth. In either case, the micro-inclusions document the presence of highly potassic fluids or melts at depths corresponding to the diamond stability field in the upper mantle. The phases presently identified in the inclusions are believed to be the result of closed system reactions at lower pressures.

Spectroscopic studies of gas-phase molecular clusters

Spectroscopic investigations of hydrogen-bonding and van der Waals' interactions m molecular clusters were studied by the techniques of infrared predissociation and resonance-enhanced multiphoton ionization spectroscopies (REMPI). Ab initio calculations were applied in conjunction for data interpretation.

The infrared predissociation spectroscopy of CN^-•(H_2O)_n (n = 2 - 6) clusters was reported in the region of 2950 - 3850 cm^(-1). The hydrogen bondings for the C-site and N-site binding, and among the water molecules were identified for n = 2 to 4. A spectral transition was observed for n = 5 and 6, implying that the anion was surface-bound onto the water aggregates in larger clusters.

The infrared predissociation spectroscopy of Br^-•(NH_3) and I^-•(NH_3)_n (n =1-3) clusters was reported in the region of 3050-3450 cm^(-1). For the Br^-•(NH_3) complex, a dominating ionic NH stretch appeared at 3175 cm^(-1), and the weaker free NH stretch appeared at 3348 cm^(-1). The observed spectrum was consistent to the structure in which there was one nearly linear hydrogen bond between Br^- and the NH_3 moiety. For the I^- •(NH_3) complex, five distinct IR absorption bands were observed in the spectrum. The spectrum was not consistent with basic frequency patterns of three geometries considered in the ab initio calculations - complex with one, two and three hydrogen bondings between I^- and the NH_3 moiety. Substantial inhomogenous broadening were displayed in the spectra for I^-•(NH_3)_n (n =2-3), suggesting the presence of multiple isomers.

The REMPI spectroscopy of the bound 4p ^2П 1/2 and ^2П 3/2 states, and the dissociative 3d ^2Σ^+ 1/2 state in the Al•Ar complex was reported. The dissociative spectrum at Al^+ channel suggested the coupling of the 4p ^2П 1/2,3/2 states to the repulsive 3d ^2Σ^+ 1/2 state. The spin-electronic coupling was further manifested in the dissociative Al^+ spectrum of the 3d ^2Σ^+ 1/2 state. Using the potential energy curves obtained from ab initio calculations, a bound → continuum Franck-Condon-intensity simulation was performed and compared with the one-photon 3d ^2Σ^+ 1/2 profile. The agreement provided evidence for the petturbation above the Al(3d)Ar dissociation limit, and the repulsive character of the 3d ^2Σ^+ 1/2 state.

Combustion of CS₂/O₂ in a laminar mixing layer and processes in the CO chemical laser

The combustion of CS₂ and O₂ in a free burning laminar mixing layer at low pressure was investigated using emission spectroscopy. The temperature fields, CO vibrational distributions, and CO concentrations were measured. The data indicate that vibration ally excited CO was produced in the mixing layer flames, but that there were no vibrational population inversions. In comparison with the CS₂/O₂ premixed flames, the mixing layer flames favored greater production of COS and CO₂. Computer modeling was used to study the mechanisms responsible for the production of COS and CO₂, and to study how the branching chain mechanism responsible for production of CO affects the behavior of the mixing layer flame. The influences of the gas additives, N₂O, COS, and CNBr, were also investigated.