High resolution color center laser kinetic spectroscopy has been used to study the kinetics and spectroscopy of free radicals. The radicals are produced in a flowing system by the excimer laser photolysis of stable precursors. The transient infrared absorptions of the radicals are monitored with better than 1 $\mu$s time resolution. Spectra of the ethynyl radical (C$\sb2$H), produced by photolysis of acetylene, were collected between 3000 and 3600 cm$\sp{-1}$ with a goal of identifying the CH stretching fundamental of the molecule. A number of new bands of C$\sb2$H and its carbon-13 analogue ($\sp{13}$C$\sp{13}$CH) were observed and rotationally analyzed. These bands include three C$\sb2$H bands of $\sp2\Sigma\sp+$ + $\gets$ $\sp2\Sigma\sp+$ symmetry, one C$\sb2$H band of $\sp2\Pi$ $\gets$ $\sp2\Pi$ symmetry, three $\sp{13}$C$\sb2$H bands of $\sp2\Sigma\sp+$ + $\gets$ $\sp2\Sigma\sp+$ symmetry, and one $\sp{13}$C$\sb2$H band of $\sp2\Pi$ $\gets$ $\sp2\Pi$ symmetry. A number of $\sp{13}$C analogues of $\sp{12}$C$\sb2$H bands were identified. However, no conclusive assignment has been made for the CH stretch. Two tentative assignment schemes are given for several of the bands. The kinetics of the C$\sb2$H + O$\sb2$ reaction were studied with a goal of determining the reaction products. OH radicals were determined to be a minor product of this reaction. Experiments designed to determine the relative importance of the hydrogen atom producing channel were inconclusive. In other kinetic studies, a high temperature furnace was constructed to determine the temperature dependences of the product channels of the NH$\sb2$ + NO reaction. The reaction was initiated by the photolysis of NH$\sb3$ in the presence of NO. The branching ratios of the OH and H$\sb2$O producing channels were determined at 26, 400, 700, and 925$\sp\circ$C by comparison of the increase in OH and H$\sb2$O absorption signals with the decrease in an NH$\sb3$ absorption signal. Branching ratios were calculated from the raw signals by using the infrared cross sections of the molecules, measured in separate experiments. The branching ratio of the OH channel is 14% at room temperature and increases to 25% at 925$\sp\circ$C. The total of the two channels (OH plus H$\sb2$O) accounts for 100% of the reaction at room temperature; however, this number drops to about 80% for higher temperatures, possibly indicating the onset of another channel.

Synthesis techniques of carbon arc and laser vaporization in the furnace for production of fullerenes have been developed. The optimum conditions for the high yields of fullerenes were tested and studied. A fullerene growth model was proposed to explain the formation of the fullerenes and the extraordinary high yield of C$\sb{60}$. The results of a test of this growth model was in agreement with the implications of the model. The electronic spectra of neutral C$\sb{60}$ and C$\sb{70}$ in the regions from 375 to 415 nm and 595 to 640 nm have been studied in a supersonically cooled molecular beam by resonant two-photon ionization spectroscopy method. Sharp spectral features were observed in both regions for C$\sb{60}$ and in only the longer wavelength region for C$\sb{70}$. Neither molecule has the spectra that correspond to the diffuse interstellar bands. The first method to produce macroscopic quantities of internal metal-doped fullerenes was developed successfully and improved. Lanthanum-doped fullerenes were produced by laser vaporization of a lanthanum oxide/graphite composite rod in a flow of argon at 1200$\sp\circ$C. Many properties of these endohedral complexes were investigated in detail. Similar results were obtained with yttrium-doped fullerenes, and double-doped endohedral fullerene complexes were first observed as a stable species in both sublimed film and toluene solution. Macroscopic quantities of other interesting metal-doped or B-doped fullerenes have been obtained and studied. Purification of these metal-doped fullerenes is in the process.

A new apparatus capable of combining an external laser vaporization supersonic cluster beam source with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been designed and implemented. Cluster ions generated in the supersonic beam source are injected down the bore of the superconducting ICR magnet and trapped in an elongated cylindrical FT-ICR ion trap. Cluster ions can be added into the ICR cell until it is filled to capacity, ensuring a high signal to noise ratio. Using standard FT-ICR techniques, specific cluster masses can be isolated with tailored excitation pulses, reacted with various reagent gases for times as long as several minutes, and examined with a mass resolution of over one million to one. This apparatus has been used to investigate the gas phase chemistry of silicon cluster ions. A systematic study of the silicon cluster reaction rate as a function of the cluster size has resulted in several remarkable results. Large fluctuations in reactivity are observed even for clusters as large as 50 atoms. Clusters containing 20, 21, 25, 33, 39, and 45 atoms are observed to be particularly inert. This result shows that these magic number clusters must have adapted a unique structure, or possibly set of structures, that exhibit a low reactivity towards ammonia. Kinetic analysis of the rate constants suggests that these unreactive clusters lack reaction sites capable of forming a strong silicon ammonia bond and/or lack sites capable of dissociatively chemisorbing ammonia. Comparisons of the cluster reactivity with the reactivity of various silicon surface reconstructions has lead to the development of an empirical model for systematically predicting the structure of silicon clusters starting at Si$\sb{20}$. This new model, based on filled pentagonal and hexagonal shell structures similar to the carbon Fullerene molecules and incorporating well established rules for silicon surface reconstructions, predicts covalently bonded clusters with $\pi$-bonded surfaces similar to the Si(111)(2 $\times$ 1) surface. The filled-Fullerene model successfully predicts the unreactive magic number clusters as being exceptionally stable structures in which all of the cluster surface dangling bonds participate in the surface reconstruction.

A quantitative analysis of the vibrational spectra of polyatomic molecules in the high energy regime requires a determination of the proper modes that optimally describe the vibrational motions of the nuclei at these energies. Observed vibrational spectra in small polyatomics indicate substantial regularity in the vibrational motion, implying that such a set of "optimal modes"should exist. Experiments have not provided a direct means of characterizing these modes. We present a computationally efficient theoretical method for performing an optimal modes analysis of multi-dimensional vibrational eigenstates. This algorithm consists of direct numerical integration of selected projection coefficients which reveals the extent of zeroth-order character of these eigenstates and is very accurate and significantly less time-intensive than previously employed methods of analysis. Demonstration of this method is presented for the analysis of selected high energy vibrations in hydrogen cyanide, monodeuterioacetylene, and propyne. The propyne analysis demonstrates the quantum mechanical intramolecular vibrational energy redistribution process in addition to the optimal mode analysis.

High resolution infrared diode laser kinetic spectroscopy has been used to study reaction kinetics and spectroscopy of short-lived species. These unstable molecules were produced in a flowing system by excimer laser photolysis of suitable precursors. Their concentrations were monitored using an infrared diode laser with fast InSb detectors. Time resolution of better than 1$\mu$s was achieved. HNO production is predicted by the reaction sequence NH$\sb2$ + NO $\to$ HN$\sb2$ + OH, HN$\sb2$ + NO $\to$ HNO + N$\sb2$ in the Miller mechanism for the thermal deNOx process. A search was made for the HNO molecule in the reaction system NH$\sb2$ + NO at room temperature using diode laser infrared kinetic spectroscopy to search for NH stretch absorptions of HNO. No HNO attributable to the deNOx process was observed. Sensitivity calibration measurements using known amounts of HNO produced from the reaction of HCO with NO were used to set an upper bound of 1% for the conversion of NH$\sb2$ into HNO. The high resolution infrared spectrum of the heavy atom antisymmetric stretch of the ketenyl radical (HCCO) was observed by means of infrared kinetic spectroscopy. Ketenyl was produced by 193 nm photolysis of ketene. The resulting transient absorption was probed with an infrared diode laser. Individual rovibrational transitions have been identified and molecular parameters have been determined from a least-squares fit of the data. The band origin is located near 2023 cm$\sp{-1}$. Acquisition of ketenyl infrared spectra allowed for determination of reaction rate constants by directly observing ketenyl decay. Kinetic studies of the ketenyl radical's reaction with nitric oxide, oxygen, acetylene and ethylene were conducted. A second order rate constant of 4.4(10) $\times$ 10$\sp{-11}$ cm$\sp3$molecule$\sp{-1}$s$\sp{-1}$ was obtained for the reaction with NO and a second order constant of 6.5 $\times$ 10$\sp{-13}$ cm$\sp3$molecule$\sp{-1}$s$\sp{-1}$ was obtained for the reaction with O$\sb2$. Acetylene appeared not to react with the ketenyl radical. An upper limit of 3.8 $\times$ 10$\sp{-13}$ cm$\sp3$molecule$\sp{-1}$s$\sp{-1}$ for the rate constant was determined by measuring the ketenyl decay in the presence of acetylene. The addition of ethylene appeared to slow the ketenyl decay. This behavior was attributed to the reaction of ethylene with a chemical species (probably H atoms) responsible for depletion of ketenyl.

Photophysical and optical imaging studies were performed on fullerene molecular complexes and individual single-walled carbon nanotubes (SWNTs). First, we investigated the reversible dimerization reaction of the newly discovered isomer of C60 oxide, [5,6]-open C60O. This oxide was found to undergo spontaneous dimerization in solution to form a new isomer of C120O2, which was structurally and photophysically characterized. This C120O2 compound can be easily converted back to its [5,6]-C60O precursor under optical irradiation. These compounds represent a unique fullerene system in which composition can be easily controlled through adjustment of concentration, temperature, and light exposure. Further, we describe a new aspect of fullerene-porphyrin interactions. The effect manifests itself in a vast increase of the fullerene triple-singlet radiative rate. Strong emission, that is C70 phosphorescence, appears in the near-infrared (NIR) wavelength region. We carefully characterized C 70-palladium octaethylporphyrin (PdOEP) supramolecular interactions and also found a similar effect with other fullerenes. The complex formation mechanism and its photophysical characterization are described. Third, we present NIR-fluorescence microscopy as a versatile method to visualize and study individual SWNTs. We demonstrate observation of individual nanotubes in a variety of environments including solid polymeric films and liquid media. SWNT identities are confirmed with spectroscopic and optical anisotropy measurements. Also, we demonstrate optical length measurements of individual nanotubes that were at least several micrometers long. Emission spectra of different parts of a single nanotube have been examined for the first time. Finally, we discuss future uses of SWNTs as novel nanoscale fluorescence markers. They supersede conventional fluorophores, which are fluorescent dyes or quantum dots (QD), in terms of both optical anisotropy and photostability. The relative ease of their detection allows one to perform a number of studies at the single nanoparticle level. Unrestricted translational and rotational motions of SWNTs are recorded and analyzed. The observed variation of translational diffusion coefficients reflects the length distribution of SWNTs in the sample. Rotational diffusion constants were found to correlate well with SWNTs translational coefficients. Promising directions for future research are outlined.

This thesis is divided into two sections. The first section focuses on the IR spectroscopic determination of the CD/CH vibrational energy spacings of the quasilinear HCCN and DCCN nu5 bending mode. We have developed an in-house program to analyze and assign the HCCN and DCCN spectra. The program has three functions, namely, spectral contour simulation, P and R transition strength calculation, and diagnostic least squares fitting. The spectral contour simulation was the most valuable tool. It generated the Q contours of transitions between various states for comparison with the observed spectra. Overall, we have successfully assigned the HCCN and DCCN nu1+2nu 5+/-2←nu5+/-1, nu 1+3nu5+/-3←2nu5 +/-2 combination bands and the HCCN nu1+3nu 5+/-3←3nu5+/-3 hot band. Using this assignment with the previous published hot band analysis, 18,19 we determined the HCCN 2nu5+/-2←nu 5+/-1, 3nu5+/-3←2nu 5+/-2 and DCCN 2nu5+/-2 ←nu5+/-1 vibrational energy gaps to be 212.821, 272.864 and 133.106 cm-1, respectively. The second part of the thesis focuses on the design and development of a supersonic jet cooling system. This system aims to expand our high-resolution IR spectroscopic work to cover much larger and more non-rigid species. A similar attempt was made a decade ago; however, the prototype was not sufficiently reliable to pass the testing stage. This project expands on our previous effort and focuses on designing a more reliable and better-performing system. We replaced the home-made pulsed valve with a more reliable commercial valve and greatly reduced the maintenance time and enhanced the ease of operation. To increase the efficiency of radical generation, we adopted the novel slit discharge method25 in place of the photolysis approach. Finally, we used a more compact and stable Herriott multipass cell design to overcome the signal broadening and averaging effects introduced by the previous White-type multipass cell. Overall, we have made much progress in enhancing the stability and performance of the system.

Two studies were performed using crossed molecular beams. The first system studied was the reaction $\rm Na\sp* + KBr \to NaBr + K\sp*,$ determining how fine structure is transmitted through a reactive collision. Each fine structure state of Na$\sp*(3\sp2$P) is separately laser excited, and the fluorescence from the two fine structure states of K$\sp*(4\sp2$P) are separately monitored. The observed K* fine-structure state distributions were not simply statistical. While the product K* fine-structure states were statistically populated for excitation to Na$\rm\sp*(P\sb{1/2}),$ they were not for excitation to Na$\rm\sp*(P\sb{3/2}).$ These distributions were interpreted in terms of nonadiabatic interaction along different regions of the KBrNa molecular potential energy surfaces. These nonadiabatic interactions were also used to help explain the differing fine-structure state populations produced in the previous NaBr + K transition state spectra. A hyperthermal seeded supersonic alkali atom source was designed and constructed for use in collisional ionization experiments. The intensity of the new source was found to be ${\approx}10\sp5$ greater than the previous charge exchange source in the energy range of interest. This source was then used to determine preliminary appearance thresholds for collisional ionization between potassium and rubidium atoms and some molecules. From the thresholds, electron affinities for SF$\sb6$ and CF$\sb3$Br and the bond dissociation energy for the CH$\sb3$Br bond could be obtained. These values were in good agreement with the literature values, although the electron affinity for CF$\sb3$Br was slightly higher (1.06 $\pm$ 0.10 eV) than the previous result in the literature (0.91 $\pm$ 0.20 eV). The effect of electronic excitation of the alkali atom on collisional ionization was also explored. The cross section for the reaction of excited state $\rm Rb\sp* + SF\sb6$ appears to be less than that for the ground state reaction. This reduction in cross section suggests that the excited state crossing can be considered to be nearly completely nonadiabatic for the experimental conditions. This result was reproduced in Landau-Zener calculations of the nonadiabatic probabilities and the ratio of the cross sections.

A non-hydrolytic synthetic method has been developed to produce unagglomerated nanocrystalline oxides, particularly titania and zirconia, which do not have hydroxyl groups on the surface. These non-hydrolytic samples display retarded grain growth rates compared to equivalent hydrothermal nanocrystalline titania and zirconia. It is demonstrated that the rate difference can be attributed to both surface chemistry and the level of agglomeration.

The tremendous increase in Raman-scattered photons seen in Surface-Enhanced Raman Scattering (SERS) has led to its adoption as a common analytical laboratory tool in spite of lingering questions about the phenomenon. One recent example is the demonstration by Jackson, et al., of SERS for silver nanoshells each consisting of an inner silica sphere encased in a silver shell. In concert with these experiments, the current investigation is directed at quantum mechanical calculation and modeling of the SERS signals to be expected for silver nanoshells coated by molecules based on ab initio calculations on an AgPMA salt model with the thiol bonding to silver rather than an H atom as in the free PMA molecule. We take the information from these calculations and consider a density matrix formalism including the effects of the strong electromagnetic near fields around the metal surface, the molecules' orientation and energy, and the associated Raman spectra.