Lifetimes of the lowest triplet electronic states of C$\sb{60}$ and C$\sb{70}$ have been studied in room temperature benzene solution. The lowest energy triplet state (T$\sb1$) of each species was formed by intersystem crossing from a laser-excited singlet state. Transient triplet-triplet absorption spectroscopy was then used to measure the decay kinetics of the triplet state. The data were analyzed using an expanded kinetic model of C$\sb{60}$ and C$\sb{70}$ triplet relaxation in solution. This model includes not only unimolecular $\rm T\sb{1}\rightarrow S\sb0$ radiationless relaxation, but also three bimolecular quenching processes: triplet-triplet annihilation, oxygen quenching and self-quenching. Under experimental conditions that suppress these bimolecular quenching processes, the exponential lifetimes of T$\sb1$ are found to be $\rm 133\ \mu s\ for\ C\sb{60}\ and\ >2.2\ ms\ for\ C\sb{70}$. Triplet C$\sb{60}$ and C$\sb{70}$ are self-quenched with rate constants of $\rm 1.5\ x\ 10\sp{7}\ M\sp{-1}s\sp{-l} and\ 8.5\ x\ 10\sp{7}\ M\sp{-1}s\sp{-l}$, respectively. Triplet-triplet annihilation occurs with bimolecular rate constants of $\rm 5.4\ x\ 10\sp{9}\ M\sp{-l}s\sp{-l}\ for\ C\sb{60}\ and\ 1.2\ x\ 10\sp{10}\ M\sp{-l}s\sp{-l}\ for\ C\sb{70}$. Mixed solutions of C$\sb{60}$ and C$\sb{70}$ are found to exhibit unusual kinetics. A kinetic model featuring efficient and reversible electronic excitation transfer between nearly isoenergetic triplet states is quantitatively successful in accounting for the observed behavior. Energy transfer rate constants for each energy transfer step have been determined from data spanning a range of sample compositions. The deduced values are $\rm 2.4\ x\ 10\sp{9}\ M\sp{-l}s\sp{-l}$ for energy transfer from $\rm C\sb{60}(T\sb{1})\ to\ C\sb{70}(S\sb{0})\ and\ 2.1\ x\ 10\sp{9}\ M\sp{-1}s\sp{-1}$ for energy transfer from $\rm C\sb{70}(T\sb{1})\ to\ C\sb{60}(S\sb{0}).$ These values imply that T$\sb1$ excitation requires only 103 $\pm$ 30 cm$\sp{-1}$ more energy for C$\sb{60}$ than for C$\sb{70}$. The long unimolecular lifetimes and rapid energy pooling may permit more efficient scheme for fullerene photochemistry and optical limiting.

Reduced-temperature synthesis of single-wall carbon nanotubes (SWNTs) is of interest for their growth into device architectures and their efficient bulk production. For SWNT synthesis, a high vacuum reactor chamber is built, in which SWNTs are grown via the chemical vapor deposition (CVD) of low-pressure ethylene over iron particles supported on silicon wafers at temperatures down to 550°C. The grown SWNT structure and quality are confirmed by atomic force microscopy (AFM) and micro-Raman spectroscopy to be good quality. SWNT growth kinetics is briefly studied. The nucleation rate depends on the ethylene pressure, which indicates that the arrival of ethylene on the iron surface is the rate-limiting step. The structural and optical properties of gold nanorods suggest their potential uses for the biomedical sensing, imaging, and therapeutic applications. Gold nanorods have been stabilized, conjugated to antibodies, and characterized for biological applications. The stabilizing surfactant cetyltrimethylammonium bromide (CTAB) bilayer which surrounds gold nanorods is replaced by thiol terminated methoxypoly(ethylene glycol) so that the nanorods are stable in buffer solutions free of surfactant. Nanorod bioconjugation is accomplished with a heterobifunctional cross-linker, with antibody activity confirmed by a strip plate assay. The molar extinction coefficient for nanorod with l = 50 nm and d =15 nm is measured to be 4.4 +/- 0.5 x 109 M-1cm-1. Gold nanorod substrates have been fabricated for Localized Surface Plasmon Resonant (LSPR) biosensors. Nanorod shows Surface Plasmon Resonant sensitivity about 180 run per refractive index unit. With nanorod LSPR sensors, we measure the surface affinity constant for biotin-streptavidin interaction and the limit of detection about 0.2 nM of streptavidin. Nanorod growth kinetics has been investigated at the microscopic level. We have shown a simple spectroscopic method to determine the microscopic length and diameter of gold nanorods during synthesis. The temperature dependent growth rate indicates that the nanorod growth follows reaction-limited growth kinetics. We also study the gold nanorod growth mechanism on surface. There is a critical size for a particle to nucleate a nanorod. This critical size is same for surfactants with different chain length. The chain length does, however, affect the isometric growth rate, which is faster for the shorter chain.

First, the parameter-dependent zeroth-order basis (PDZOB) method was employed in the study of the quantum mechanical dynamics of a HCN/HNC isomerization model reaction for a few hundred femtoseconds before the time of the unimolecular reaction. From this study, it was learned that the dominant mode-mode specific energy flow incorporated with large and sudden energy transfer is responsible for the isomerization. The classical dynamics study of the same isomerization also reveals the mode-mode specific impulsive energy transfer. Second, the HEG-Wigner distribution (HEGWD) method was applied to study phase space in the quantum dynamics of a two-mode hindered rotor isomerization. We discovered that regularity in the phase space lasts for about 200 fs after the initiation of this reaction. Strong correspondence between the semi-classical result with $\hbar$ = 0.5 and that in the classical result has been observed; however, there was no clear correspondence between the full-quantum result with $\hbar$ = 1.0 and the classical result.

A preliminary temperature-programmed desorption (TPD) study of hydrogen desorbing from diamond (100) concludes that the previously-reported non-saturation behavior of the surface is an experimental artifact resulting from desorption from the Ta heater. Critical conditions for conducting an accurate TPD measurement are identified. In its first application to the diamond surface study in which lateral periodic boundary conditions are incorporated, the molecular mechanics method (MM3) has been shown to be a useful tool in determining surface structures and energetics, employing modest-sized clusters. Atomic structures and energetics of the diamond (100)-(2$\times$1), (100)-(2$\times$1):H, (100)-(1$\times$1):2H, and (100)-(3$\times$1):1.33H surfaces have been calculated. Pairs of surface carbon atoms form symmetric dimers on the reconstructed diamond (100)-(2$\times$1), (100)-(2$\times$1):H, and (100)-(3$\times$1):1.33H surfaces, with dimer bond lengths of 1.46 A, 1.63 A, and 1.59 A, respectively, corresponding to strained double or single bonds. The full (100)-(1$\times$1):2H dihydride is highly strained due to H-H repulsions, causing a reduction of the H--C--H bond angle and twisting about the surface normal, and is predicted to be thermodynamically unstable with respect to dehydrogenation to the monohydride. Some important gas-surface reactions involving hydrogen and the diamond (100) and (100)-(2$\times$1):H are discussed in light of the derived energetics. We have noted that preferential pairing of chemisorbed hydrogen on Si(100) is a direct result of the partial $\pi$-bond existing on the surface dimers. A lattice-gas model has been developed based on this concept, and predicts that, with a modest pairing energy, hydrogen desorption adopts near-first-order kinetics at high coverages but deviates from first-order kinetics at low coverages. We calculated the pairing energy of adsorbed H to be about 7.5 kcal/mol, based on a comparison of the predictions of the model with experiment. We conclude that preferential pairing on dimers is a general feature of hydrogen adsorption on the (100) surfaces of group IV semiconductors.

Single photon vibrational absorption spectra of hydrazoic acid (HN$\sb3$, hydrogen azide), a model unimolecular reactant, have been recorded in the 500-22500 cm$\sp{-1}$ spectral region. Vibrational spectra of nitrous oxide (N$\sb2$O), an isoelectronic analogue of HN$\sb3$, have also been recorded in the 500-15200 cm$\sp{-1}$ spectral region. At high vibrational energy (above thresholds of approximately 12600 and 18500 cm$\sp{-1}$), HN$\sb3$ exhibits vibrational and/or electronic predissociation to form two sets of products (N$\sb2$ + NH(X$\sp3\Sigma$), NH*(a$\sp1\Delta$)) that evolve from the reactant on multiple potential energy surfaces. Spectral line broadening measurements on highly vibrationally excited states of hydrazoic acid have been performed to determine intramolecular lifetimes for vibrational predissociation and other intramolecular rate processes. Thousands of rovibronic transitions have been analyzed to yield accurate spectroscopic (rotational, vibrational) constants of NH stretch vibrational overtone states (up to 7$\nu\sb{\rm NH}$) and of combination states involving NH stretch overtone excitations plus one or more quanta of other vibrational modes. Absolute and/or relative absorption intensities have been measured for many vibrational bands. Extensive high resolution linewidth measurements on individual rovibronic transitions as well as spectral simulations of the linewidths of strongly overlapping transitions have been completed in order to determine lifetime broadening rates and mechanisms as a function of rovibronic excitation energy and state both below and above characteristic predissociation thresholds. Initial single photon vibrational photochemistry experiments on HN$\sb3$ have also been completed. Single photon vibrational excitation of HN$\sb3$ overtone (5$\nu\sb{\rm NH}$ and 6$\nu\sb{\rm NH}$) and combination band states was performed using intracavity dye laser absorption techniques. Sensitive detection of HCN and NH$\sb3$ secondary products (generated by reaction of NH primary photochemical products with ethylene) was performed using intracavity photoacoustic spectroscopy techniques. Possible mode dependent reactions were explored. All of the data reported have been used to consider the nature and dynamics of highly vibrationally excited hydrazoic acid in bound as well as in predissociative regions of HN$\sb3$ potential energy surfaces.

Laser photofragmentation of Si, Ge, and GaAs positive cluster ions prepared by laser vaporization and supersonic beam expansion has been investigated in a tandem time-of-flight mass spectrometer. Si$\sb{\rm n}\sp +$ up to size 80, Ge$\sb{\rm n}\sp +$ and Ga$\sb{\rm x}$As$\sb{\rm y}\sp +$ up to a total of 31 atoms have been studied. Ga$\sb{\rm x}$As$\sb{\rm y}\sp +$ fragment in a nearly uniform pattern probably via a step-loss of atoms pattern with odd fragments being more prominent than their even neighbors. Both Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ of all sizes show as one fragmentation channel loss of one atom to produce Si$\sb{n-1}\sp +$ or Ge$\sb{n-1}\sp +$. In addition, Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ in the size range n = 10-30 photofragment to produce positive ions of about one half the mass of the parent. For Ge$\sb{\rm n}\sp +$ as n becomes greater than 30, this fragmentation becomes a pattern in which positive ions containing 10 (or 7) fewer atoms are the principal products at low laser fluence. Increased fluence seems to fragment these daughters in the same way as they would behave as primary ions. The Si$\sb{\rm n}\sp +$ ions of greater than 30 atoms do not show this 10 or 7 atom neutral loss. Both Si$\sb{\rm n}\sp +$ and Ge$\sb{\rm n}\sp +$ for n $>$ 30 show an additional channel in which small positive ion fragments in the n = 6 to 11 size range are produced. This channel requires high fluence and is shown to involve at least two 6.4 eV (ArF) photons for Si$\sb{60}\sp +$. The absence of intermediate fragments in this channel suggests that these large cluster ions break down into several clusters because the positive charge would be expected to stay with the larger fragment in a fission into two clusters as the ionization potentials of the neutral clusters decrease with size. A reflectron tandem time-of-flight mass spectrometer has been designed and constructed. The resultant high resolution makes the apparatus a highly efficient instrument for fragmentation and spectroscopic studies.

Equilibrium concentrations of the major species in conventional and halogen assisted CVD diamond synthesis systems were calculated and the results are presented in this thesis. The optimal diamond deposition conditions were predicted based on these calculations and kinetic considerations as well. The calculations suggest that the addition of chlorine or fluorine can significantly reduce the temperature of CVD diamond deposition. The step growth mechanism on a diamond (001) surface was also investigated using molecular mechanics calculations (MM3). The basic step in diamond growth was found to be the incorporation of a gas phase carbon species such as the methyl radical into two carbon atoms on the surface which involves the breaking of the original dimer bond and the formation of a new one. It is suggested that only growth on the S$\sb{\rm B}$ step can continuously generate a smooth (001) surface while individual dimer rows extending from the S$\sb{\rm A}$ step or random dimer rows are kinetically unstable. The mechanism presented in this thesis explains the recent STM observations of finger growth patterns which extend from the SB step on the diamond (001) surface.

Studies of the slow pyrolysis of coals using matrix-isolation Fourier-transform infrared spectroscopy (MI-FTIR) and electron spin resonance (MI-ESR) have given insight to coal structures. Evolution of light carbonyl compounds below 250$\sp\circ$C and dealkylation reactions to form light hydrocarbons occurred from 150-400$\sp\circ$C. CH$\sb4$ evolution continued to 800$\sp\circ$C. Hydroxyl group decomposition evolved H$\sb2$O from 150$\sp\circ$C to 700$\sp\circ$C. Tar evolution began at 150$\sp\circ$C with maximum production from 300-600$\sp\circ$C. H$\sb2$S evolved with the tar fraction at 300-500$\sp\circ$C. CS$\sb2$ evolved from 800-1200$\sp\circ$C. SO$\sb2$ from sulfate decomposition was most notable for Pittsburgh and Illinois #6, less so the lower range coals. Nitrogen pyrolysis products were NH$\sb3$ at 300-700$\sp\circ$C and HCN at 3500-800$\sp\circ$C. C$\sb2$H$\sb2$ was formed from 950-1400$\sp\circ$C. Kaolinite reduction yielded SiO, Al$\sb2$O, and aluminum atoms complexed with CO at 1150-1500$\sp\circ$C. Two distinct hydroxyl groups at 3626 cm$\sp{-1}$ and 3581 cm$\sp{-1}$ were detected in a N$\sb2$ matrix for tars evolved from 300-600$\sp\circ$C. These groups were identified as phenolic hydroxyls and were most prevalent in Pittsburgh and Illinois #6. O-methylation of the carboxyl, aliphatic and phenolic hydroxyl groups in coal changed the pyrolysis behavior. Esters, aromatic ethers, and aliphatic ethers were observed in FTIR spectra of KBr methylated (CD$\sb3$I) coals. Pittsburgh and Illinois #6 contained phenolic-OH groups with some COOH groups and fewer aliphatic-OH groups. Rawhide and Texas Lignite contained more phenolic-OH than COOH and aliphatic-OH. Methanol and formaldehyde were produced from ester and aliphatic ether decomposition whereas methane and carbon monoxide evolved from aromatic ethers. MI-ESR studies indicated peroxy radicals in evolved tars which can be attributed to surface peroxides. Pittsburgh and Illinois #6 tars displayed two radicals, one with average g values of 2.0366, 2.0071 and 2.0014 and the other 2.0302, 2.0098 and 2.0014. MI-FTIR studies showed a marked influence on the pyrolysis behavior of Pittsburgh for CaO and to a lesser extent MgO. The phenolic hydroxyl at 3626 cm$\sp{-1}$ was decreased when Pittsburgh was pyrolyzed with CaO and a large amount of water preceded the tar evolution. For all additives tar was evolved at higher temperatures indicating their ability to change the mechanism of tar evolution.

A fundamental question in the chemistry of azoalkanes concerns the nature of their primary bond cleavage: do the two C-N bonds break in a synchronous or a sequential fashion? The photodissociation of an acyclic, unsymmetrical azoalkane, 3-(methylazo)-3-methyl-1-butene (MAMB), was studied using time-resolved coherent anti-Stokes Raman spectroscopy (CARS) to probe for product formation. Appearance kinetics were measured for all three primary photoproducts following excitation. The 3-methyl-1-buten-3-yl radical fragment appeared within 2 ns of excitation, while the methyl radical and N$\sb2$ were formed through decay of a reaction intermediate (the methyldiazenyl radical) having a lifetime of 12 $\pm$ 2 ns. These results directly demonstrate sequential photodissociation. Similar investigations of photodissociation in the bicyclic azoalkane, 2,3-diazabicyclo (2.2.1) hept-2-ene (DBH), were also performed. After excitation to S$\sb1$, DBH dissociated to form N$\sb2$ and a biradical, 1,3-cyclopentadiyl which was observed to decay through ring closure with a lifetime of 235 $\pm$ 50 ns. The nitrogen photoproduct shows an appearance that has a risetime of 20 $\pm$ 5 ns. The nascent vibrational distribution of the nitrogen photoproduct was found to be 82 ($\pm$4)% in v = 0, 13 ($\pm$4)% in v = 1, and 5 (+2/$-$4)% in v = 2, giving a value of 535 cm$\sp{-1}$ for its average vibrational energy content. Observations of the vibration-rotation contour of the precollisional nitrogen revealed a rotational population distribution peaked at low values of J. Such a distribution suggests a transition state in which both C-N bonds are equally stretched and symmetric forces act on the nitrogen centers as the fragments separate. Fluorescence from DBH vapor excited to its S$\sb1$ origin was directly observed to have a rapid dual exponential decay, implying that DBH undergoes an intermediate-case radiationless transition to discrete levels of T$\sb1$ within 5 ns. A photochemical mechanism proposed to explain these findings involves single-step electronic predissociation of DBH from its T$\sb1$ surface to form N$\sb2$ plus triplet 1,3-cyclopentadiyl biradical. By contrast, acyclic azoalkanes are suggested to dissociate through a competing two-step process whose initial step occurs from a twisted T$\sb1$ structure that is not accessible in DBH.

This dissertation describes a series of photophysics experiments on buckminsterfullerene (C$\sb{60}$), other fullerenes (C$\sb{\rm n}$), and the metallofullerenes (C$\sb{\rm n}$M). Photodissociation is performed in a tandem time-of-flight mass spectrometer. Mass isolated cluster ions are irradiated with a high fluence UV laser and the product ions are mass analyzed. All these clusters dissociate identically: the primary fragmentation event is loss of neutral C$\sb2$. All fragmentation is multiphoton at 6.4 eV. Higher order fragmentation is by loss of an even numbered neutral carbon particle. This production of fullerene fragments stops at C$\sb{32}$ for the pure carbon, and at a size which depends on the metal atom for the metal-carbon clusters. The fullerene product ions show stability at 50, 60, and 70, especially when produced in a long timescale metastable decay process. The spheroidal shell theory of carbon can explain all these results. This theory states that large even C$\sb{\rm n}$ clusters have edgeless spheroidal cage structures with 12 pentagons and n/2-10 hexagons. C$\sb2$ loss occurs because the transition state for C$\sb3$ loss is not accessible. Stability at clusters with 28, 32, 50, 60, and 70 is a result of spherically distributed strain of curvature. C$\sb{60}$ can perfectly distribute its strain explaining its dominance. The central cavity of these structures is large enough to complex a metal ion, but only down to a certain size.