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.

We present a study of the ground and triplet state properties of C$\sb{60}$O. UV-vis spectroscopy and a gravimetric analysis are used to produce a quantitative electronic absorption spectrum. Spectrofluorimetry reveals that the fluorescence quantum yield of C$\sb{60}$O is $8.1\times 10\sp{-4}$, which is a factor of 2.5 higher than that of C$\sb{60}$. Transient absorption spectroscopy is used to study the triplet state of C$\sb{60}$O, which is seen to exhibit complex decay kinetics. A possible explanation for this behavior involving triplet mediated epoxide ring opening is presented. The intrinsic triplet lifetime is determined to be 6.8 $\pm$ 0.3 $\mu$s, making C$\sb{60}$O the shortest lived fullerene derivative studied to date. Additional studies reveal that the decay of C$\sb{60}$O triplets has a mild temperature dependence corresponding to an E$\sb{\rm a}$ value of 4.5 $\mu$ 0.6 kJ/mol, whilt self-quenching is seen to play a negligible role. Furthermore, solutions of C$\sb{60}$O are shown to be unstable with respect to temperature, generating unknown impurities even at room temperature. Mass spectrometric studies failed to unambiguously identify the product contaminant.

Various density functional methods have been tested for the van der Waals interactions of the rare gas dimers He$\rm\sb2,\ Ne\sb2$ and Ar$\sb2$ as model compounds. Detailed analysis proved that all tested and commonly used functionals are not suitable for an appropriate description of the interactions, even if Hartree-Fock exchange is used in combination with a correlation functional. However, within the framework of long-range density functional theory, van der Waals coefficients are correctly reproduced by a density-density interaction term. Adding these interactions separately to the tested functionals, surprisingly good results are obtained by using exact exchange.

This thesis is composed of three parts. Part I describes a DFT study of the C60 dimer cations and anions which indicates that [2+2] isomers are lower in energy than single bond (SB) isomers. The center to center distances (CCD) of these two isomers calculated in our study are in fair agreement with experiment. Part II presents a good model (Fe+-oronene) and a scheme to simulate the binding of iron cations to [n, n] nanotubes. The binding energy from all DFT calculations increases as the nanotube diameter decreases, which can be explained by pi-orbital axis vector (POAV) theory. LSDA and PW91PW91 are believed to overestimate the binding energy while BPW91 and B3LYP are expected to give better results. Part III analyzes two possible patterns of fluorine addition to single wall carbon nanotube that have been proposed as 1,2 and 1,4 addition. Semi-empirical calculations indicate that the 1,4 isomer is lower in energy. Fluorine atoms prefer to grow along the tube for the 1,2 isomer whereas for the 1,4 isomer, they prefer to grow around the tube. This is consistent with results from a STM study of the fluorinated nanotubes.