The spark spectra of zinc have been photographed in the region λ350 Å to λ8000 Å using a three metre normal incidence vacuum grating spectrograph, a twenty-one foot Eagle-Paschen " in-plane" grating spectrograph, and a Hilger E478 large automatic prism spectrograph with interchangeable glass or quartz optical trains. The spectra were excited using a condensed spark in helium source, a hollow cathode discharge, and a condensed electrodeless discharge source. In all, 5982 spectral lines were measured. Sixty-four line classifications were made in Zn I from previously established energy levels. Three hundred and seventy-one line classifications were made in Zn II, and 33 new levels were established. In Zn III, major revisions and extensions have led to a total of 1259 line classifications and 264 energy levels were established, 44 of which had been determined previously. Revisions to a previous report on the spectrum of Zn IV have resulted in an increase of the number of classified lines to 329. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The static field induced absorption spectrum of hydrogen has been investigated at high resolution and with reliable frequency calibration over the density range from 1.5 amagat to 28 amagat. Frequencies have been extrapolated to zero density in order to obtain molecular constants for the isolated molecule. Line profiles have been compared with various functions and the simple dispersion profile seems to fit the data best over the density range studied. The linewidth, however, decreases with density until it reaches a minimum at about 2.5 amagat below which it starts to increase again. The minimum width is about 4 times less than the width of the classical doppler line. This behavior of the line width is consistent with the phenomena of "collision narrowing" in the infrared. From the intensities of the lines we obtain the isotropic polarizability (α )₁₋₀ = 1.21 cm³. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The design and construction of a high-resolution, low-energy and variable-angle electron impact spectrometer has enabled the study of the interaction between a low energy monochromatic electron beam and a series of atoms and molecules. Optically forbidden transitions have been studied for argon and neon. The Rydberg transitions in atoms and small molecules have also been investigated. The "vacuum ultraviolet spectra" (electron impact spectra) obtained for some organic molecules such as the alkyl derivatives of water and carbonyl compounds have been interpreted in terms of Rydberg transitions. Substituent effects on Rydberg orbital energies and ionization potentials are discussed using Taft σ* values. / Science, Faculty of / Chemistry, Department of / Graduate

Binary (e,2e) spectroscopy is an intermediate energy electron scattering coincidence technique measuring the binding energy and spherically-averaged momentum distributions of individual valence electrons in small gaseous molecules. Momentum space chemistry is a term used to refer to the study of the attributes of molecular orbitals in the momentum space representation, rather than the usual position space representation. The relation between the two spaces is the Fourier Transform. This thesis discusses experimental measurements and theoretical calculation of the binding energy spectra and/or momentum distributions of. H₂S, COS, C0₂, NO and 0₂ in detail. It also attempts to bring into the ken of ordinary chemistry concepts and principles for dealing with momentum-space molecular orbital density functions, which are essential to the understanding of the nature of momentum distributions. In order to illustrate this, specific examples of theoretical momentum and charge density maps for several molecules are discussed. Significant new understanding of the electronic structure of these molecules is attained. The design, construction, and preliminary testing of a new binary (e,2e) spectrometer incorporating a multi-channel plate detector for improved data collection efficiency is presented. Finally, some propositions for future directions of study are put forward. / Science, Faculty of / Chemistry, Department of / Graduate

A simple empirical model to calculate solar spectral diffuse and global irradiance under cloudless skies was investigated. This formulation takes into account absorption of radiation by molecules such as O3, H2O and the uniformly-mixed absorbing gases CO2 and O2. Attenuation by Rayleigh-scattering and aerosol extinction are included. Aerosol attenuation is calculated through Angstrom's turbidity parameters α and β. The diffuse radiation is assumed to be composed of three parts: (1) Rayleigh-scattered diffuse irradiance; (2) aerosol-scattered diffuse irradiance; and (3) irradiance arising out of multiple reflections between the atmosphere and the ground. The global irradiance is the sum of these three components of diffuse irradiance plus the direct irradiance. The input parameters include an extraterrestrial spectrum, zenith angle θ, turbidity coefficient β, wavelength exponent α, ground albedo p , water vapor content and ozone content. The model is shown to yield very good results up to air mass two when compared to accurate theoretical calculations. No comparisons with measured spectra are presented because of a lack of accurate specifications of the input parameters. Results are presented to show the effect of variation of certain of the input parameters. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Filter-free spectral tunable photodetectors (PDs) are critical for a plethora of applications in imaging, indoor light fidelity (Li-Fi), and light communications. The present band-selective light detection is realized by incorporating different optical filters with broadband inorganic semiconductor-based PDs. However, the use of the optical filters reduces the overall performance of these PDs and is not appliable in the emerging flexible and wearable applications. The rapid advancement of the organic semiconductors offers an exciting opportunity for the development of high-performance filter-free spectral tunable organic photodetectors (OPDs). The development of OPDs has attracted tremendous interests because of the tailored optoelectronic properties of the π-conjugated organic semiconductors and the solution fabrication process of the OPDs. Apart from the rapid progresses made in improving the responsivity and detectivity of OPDs, the spectral properties of OPDs also receive intense attention. This Ph.D. research work has been focused on developing a universal strategy to achieve high-performance filter-free band-selective and spectral tunable OPDs. The correlation between the optical profile and responsivity spectrum of the novel OPDs with a bilayer photoactive layer has been investigated. It suggests that the responsivity spectrum of the OPDs can be effectively modulated by managing the optical profile in the bilayer and multilayer photoactive layer. A filter-free band-selective OPD model, comprising a bilayer shorter-wavelength light depletion layer/longer-wavelength light-absorbing layer architecture photoactive layer, has been developed. The depletion layer in the filter-free OPDs has a dual-function serving as a shorter-wavelength light-absorbing layer and a hole-transporting layer. The photodetection spectrum window of the filter-free band-selective OPDs, defined by the difference in wavelengths between the transmission cutoff of the shorter-wavelength light depletion layer and the absorption edge of the longer-wavelength light-absorbing layer, can then be tuned over the different wavelength ranges by using an appropriate combination of the shorter-wavelength light depletion layer and the longer-wavelength light-absorbing layer. A dual-mode OPD, having a trilayer visible light absorber/optical spacer/near-infrared (NIR) light absorber configuration photoactive layer, has been proposed. The dual-mode OPD exhibits electrically switchable NIR response operated under a reverse bias and visible light response operated under a forward bias. In the presence of NIR light, the trap-assisted charge-injection behavior at the organic/cathode interface in the OPDs operated under a reverse bias. The photocurrent is produced in the visible light-absorbing layer, enabled by the trap-assisted charge injection at the anode/organic interface under a forward bias. The developed filter-free band-selective OPDs and electrically switchable dual-mode OPDs provided an attractive alternative optical detection technology to the conventional panchromatic and single-mode OPDs. The spectral tunable photodetection thus demonstrated offers a promising option for new OPD applications.

In this thesis we investigate the problem of robustness and scalability w.r.t. estimating the position of randomly deployed motes/nodes of a Wireless Sensor Network (WSN) without the help of Global Positioning System (GPS) devices. We propose a few applications of range independent localization algorithms that allow the sensors to actively determine their location with high resolution without increasing the complexity of the hardware or any additional device setup. In our first application we try to present a localized and centralized cooperative spectrum sensing using RF sensor networks. This scheme collaboratively sense the spectrum and localize the whole network efficiently and with less difficulty. In second application we try to focus on how efficiently we can localize the nodes, to detect underwater threats, without the use of beacons. In third application we try to focus on 3-Dimensional localization for LTE systems. Our performance evaluation shows that these schemes lead to a significant improvement in localization accuracy compared to the state-of-art range independent localization schemes, without requiring GPS support.

Solar energy is a viable alternative to traditional fossil fuel sources. However, single junction silicon solar cells can only efficiently absorb ~30% of available sunlight. A portion of sunlight is too low in energy to be absorbed by the solar cell while another portion of sunlight is too high in energy to be absorbed without losses due to thermalization. Singlet fission, a process that converts a high energy singlet exciton into two lower energy triplet excitons, can be used to convert high energy light into lower energy light that can be absorbed efficiently by silicon. Singlet fission materials that undergo fast singlet fission, have long lived triplets, and have long triplet diffusion lengths show the greatest potential to increase the efficiency of solar cells. This thesis describes the design and singlet fission behavior of norbornene based polymers with pendent acene chromophores. The first chapter highlights other supramolecular singlet fission materials that have been studied to date that served as inspiration for this work. The second chapter demonstrates the efficient singlet fission and the slow, molecular weight dependent triplet recombination that occurs in pendent pentacene polymers. The third chapter outlines how the tunability of the polymer can be used to control singlet fission dynamics. In the fourth chapter, the singlet fission dynamics are shown to be largely unaffected by solvent composition and by casting into thin films. The fifth and final chapter explores exciton migration in pendent tetracene and pentacene block copolymers. This thesis illustrates a new, high tunable platform for studying inter-chromophore singlet fission, which shows promise for use in solar cells.

This thesis is a study of the celestial gamma-ray flux. It reviews several of the proposed mechanisms for producing high energy gamma rays and describes several of the attempts to detect their presence. Also included is a short historical review of the spark chamber, along with a qualitative description of its operation.

CASE: A 6-year-old boy with a diagnosis of autism spectrum disorder (ASD) presented to primary care for a newpatient, transfer-of-care evaluation. At the initial encounter, the patient used a maximum of 60 words and was receiving speech and language therapy (SLT) through school. Family history was positive for seizures in the father and paternal grandfather as well as ASD in an older brother. Referrals to genetics, private SLT, and an autism specialist were offered, although the latter was declined by family. The subsequent genetics evaluation resulted in discovery of a small gain on chromosome 1q42.2 and associated partial duplication of the DISC1 gene. The assay could not determine the exact clinical significance of the abnormality, but similarly sized and located abnormalities involving the DISC1 gene are reported in some patients with ASD and developmental delay. During a follow-up pediatrics appointment, the father expressed his wish for further evaluation of causes of autism spectrum disorder (ASD) and requested an electroencephalography (EEG) evaluation. The family concomitantly reported slow improvement in speech with therapy, the use of up to 200 words, and the ability to count to 10. The primary care physician reiterated that EEG and imaging studies are not indicated for an isolated ASD diagnosis with no supporting history or physical examination indications. The clinician discussed ASD-recommended therapies with the family. Neurology referral was made per parental request. The patient subsequently presented to neurology at the age of 7 years. The parents reiterated during the initial neurologic developmental history that the patient had shown some improvement with speech and language therapy in the past 18 months, knew as many as 200 to 300 words, and could put some words together into simple sentences. Gross and fine motor development were felt to be within the normal range for age. The parents also reported some scripting, and mild echolalia was noted on examination. Notably, there was no history of language regression. Apart from language delay, the neurologic examination was otherwise normal at initial evaluation. Given this clinical picture, ASD treatment options were again discussed. Despite education, parents continued to request for EEG evaluation as a workup for the etiology of the patient's ASD. Electroencephalography was ultimately ordered owing to the strong and repeated paternal request despite denial of any seizure-like episodes in the patient. EEG unexpectedly showed extremely frequent, almost constant focal electrographic seizures arising from the T3/T5 electrodes in the speech area of the left temporal lobe, prompting the initiation of oxcarbazepine maintenance therapy. Because of the noted abnormalities on EEG, magnetic resonance imaging (MRI) was obtained. Mild abnormalities were noted on MRI study including possible minimal inferior cerebellar vermian hypoplasia, mildly prominent bodies of the lateral ventricles, and nonspecific, nonenhancing punctate T2 hyperintensities in the subcortical white matter. These findings were not felt to be clinically relevant to the patient's presentation or seizure evaluation. No repeat imaging was ordered. Hindsight is always 20/20. As a clinician evaluating the patient initially, would you have pursued further workup sooner?