Though there has long been uncertainty as to the nature of active nitrogen, the matter was in part settled in the mass-spectrometric studies of Jackson and Schiff, and Berkowitz, Chupka, and Kistiakowsky, where the only components detectable in a gas mixture at about l mm. pressure and containing about one percent active nitrogen were the ground state molecule and the 4S atom. This observation was, of course, consistent with most of the known properties of active nitrogen, in particular Wrede gauge measurements, the chemical behaviour, and the kinetics exhibited in the emission of the afterglow.

As early as 1900 the existence of active nitrogen with its accompanying afterglow had been established by Lewis. On subjecting nitrogen to a condensed discharge, he found that a yellow cloud filled the discharge tube and persisted for several seconds after the discharge was stopped. The banded spectrum produced by this afterglow was identified with the nitrogen spectrum. [...]

Strutt, in particular, made valuable contributions to the development of appropriate apparatus for the production of active nitrogen. In 1916 he published a diagram of a discharge tube apparatus in which aluminum electrodes were used, and this metal still remains the favoured electrode material for the production of active nitrogen.

The brilliant yellow afterglow shown by nitrogen activated in a discharge tube was first reported by Lewis (1) who studied its behaviour in 1900. He observed that the yellow emission persisted for several seconds after the discharge was stopped, and was able to show that this afterglow produced a banded spectrum identical with part of the N2 spectrum..

Note: / The importance of atoms and free radicals as intermediates in many chemical reactions is now becoming increasingly apparent. The transitory nature of the intermediates, ie, their comparatively short lifetimes, and their relatively low steady state concentrations, have in the past complicated the identification and elucidation of the elementary reactions in which they are involved.

The earliest indication of the importance of chain mechanisms in gaseous reactions came from the work of Bodenstein. His calculations of the quantum yields of several photochemical reactions demonstrated unequivocally that the Einstein Law of Photochemical Equivalence could not be applied to the overall processes. Nernst was one of the first to suggest that atoms were the chain carriers in these reactions, and for this reason the "Nernst Chain" - proposed for the photochemical synthesis of hydrogen chloride - still bears his name. [...]

Note: / The reaction of nitrogen atoms with propane has been found to produce hydrogen cyanide, ethane, ethylene, methane and hydrogen in the temperature range 75c. – 292c. The rate of hydrogen cyanide formation at a constant nitrogen atom flow rate increased with increasing propane flow rate; no corresponding increase was observed for the rates of formation of the other hydrocarbons. Second order specific rate constants were calculated from the rates of disappearance of propane.

<p> The goal of this thesis was to integrate light-absorbing supramolecular materials into a photocatalytic system for solar-to-fuel conversion. Toward this end, a series of perylene-based chromophore amphiphiles was synthesized and their self-assembly properties explored. Characterization of these materials by electron microscopy and x-ray scattering techniques revealed molecular assembly into 1D ribbon nanostructures. Surprisingly, these ribbons were observed to spontaneously crystallize in solution, as observed by wide-angle and grazing incidence X-ray scattering. These crystalline nanostructures could be gelled with oppositely charged electrolytes, forming a 3D light-absorbing scaffold. By designing and synthesizing oppositely charged proton reduction catalysts to electrostatically bind to the light-absorbing scaffold, hydrogen gas was detected by gas chromatography after white light illumination of the scaffold / catalyst system. As a direct result of their crystalline nature, the exciton properties of these materials and the photocatalytic properties of the system could be tuned by slight modification in their molecular packing arrangement. These changes were achieved by creating a library of chromophores with small functional groups directly attached to the PMI core. Some amphiphiles in this library were observed to undergo a crystalline phase transition between two unique packing arrangements as evidenced by variable temperature absorbance and x-ray scattering experiments. This transition involved a substantial change in the exciton properties of the material. Surprisingly, some crystalline phases carried the distinct spectral signature of charge-transfer (CT) excitons, an excitation that is shared among multiple chromophores. Characterization of this CT state was accomplished by ground state and transient absorption spectroscopy, transient electron paramagnetic resonance spectroscopy, and second-order harmonic generation microscopy. The crystalline nanostructures of the library that yielded evidence for CT-excitons were the most photocatalytically active. This observation is consistent with established theories developed elsewhere that connect CT-exciton formation with an enhancement in exciton mobility.</p>

<p> In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic <i>bricks</i> connected by organic <i>linkers</i>. From a crystal engineering stand point, MOFs are advantageous in creating a range of microporous (0.2&ndash;2.0 nm) to mesoporous (>50 nm) void cavities, presenting unique opportunities for the functionalization of both the organic <i>linkers</i> and the void. Of significant importance is the MOF-74-M family (M = metal), characterized by a high density of open metal sites, that is not fully coordinated metal centers. This family of MOF is also known as CPO-27-M. MOF-74 have demonstrated more separation potential than other known MOFs and zeolites. Density functional theory (DFT), as implemented within a linear combination of atomic orbital (LCAO) approach, has been used to investigate the selective sorption of C1-C4 hydrocarbons in MOF-74-Mg/Zn. The study was first implemented by adopting a molecular cluster approach, and later by applying periodic boundary conditions (PBC). While both modellistic approaches agree in showing significant differences in binding energies between olefins and paraffins adsorbed at the MOFs&rsquo; open metal sites, results reported at the molecular cluster level show underestimation when compared to those obtained at the PBC level. The use of PBC models allow for the correcting of binding energies for basis set superposition error (BSSE), molecular lateral interaction (LI), zero-point energy (ZPE), and thermal energy (TE) contributions. As such, results obtained at the PBC level are directly comparable to experimental calorimetric values (<i>i.e</i>., heat of adsorptions). This work discusses, for the first time, the origin of the fictitious agreement between binding energies obtained with molecular clusters and experimental heats of adsorption, identifying its origin as due to compensation of errors. Spectroscopy studies based on the intensities and frequency shifts with respect to the molecules in the gas phase are presented as a further investigation of the interaction of the small hydrocarbons (C₁-C₂) with the open metal sites in MOF-74-Mg. In an attempt to provide a more comprehensive description of the behavior of the hydrocarbon molecules, results from diffusion mechanism studies are also presented. The investigations of the diffusion mechanisms are based on the use of climbing-image nudge elastic band (CI-NEB) simulations, coupled with van der Waals functional (vdW-DF) and ultra-soft pseudopotentials as implemented within the plane-wave (PW) DFT approach. The CI-NEB studies showed that paraffin molecules are more energetically favored to diffuse within and along the cavity of MOF-74-Mg with respect to their olefin counterparts.</p><p>

<p> The Pauli Exclusion Principle ensures that orbital occupations arise from a physically real- istic quantum system. There are additional conditions, motivated by quantum information theory, that are necessary for electron occupations to arise out of pure quantum states that are said to generalize the Pauli principle. Our work with Generalized Pauli conditions has lead us to develop electronic structure theories that are able to, <i>i</i>) recover many-body correla- tion energies, <i>ii</i>) derive sufficient conditions for openness in a quantum system, <i>iii</i>) formulate a geometric perspective on energy transfer, and, <i>iv</i>) highlight the structural complexity of excited state spectra, from one-electron theories.</p><p>