Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"astrochemistry"”.
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Quantum Mechanical Study of Spin-Forbidden Reactions in Organometallic Catalysis and Astrochemistry
This dissertation presents a quantum mechanical investigation of spin-forbidden reactions in organometallic C-H bond activation and interstellar peptide-bond formation, as well as the derivation of the Morse empirical potential from an electrostatic model. In the first part, the role of triplet …
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Machine Learning Estimation of Reaction Energy Barriers and its Applications in Astrochemistry
We developed a machine learning model for fast estimating reaction energy barriers. The model was trained on data for 11,730 elementary reactions and barriers computed with an estimated accuracy of 2.3 kcal/mol by Grambow and coworkers. Although it was trained, and then applied, only for reactions …
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Chemical physics and astrochemistry of H3+ and sub Doppler mid infrared spectroscopy of molecular ions
Molecular ions are known to be key reactive intermediates in interstellar environments, and H3+ in particular is responsible for initiating a network of chemical reactions that ultimately results in the formation of the ~170 molecules detected so far in space. Yet fundamental questions about the …
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Experimental investigations of molecules desorbing from a cold surface with buffer gas cooling and broadband roational spectroscopy : applications in astrochemistry
This thesis presents the description of a novel instrument which couples buffer gas cooling with chirped-pulse Fourier transform mm-wave rotational spectroscopy and its successful applications in the study of molecules desorbing from an ice under interstellar-like conditions. The instrument, …
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New techniques for sub-Doppler spectroscopy of molecular ions
… are of interest to a variety of fields, from astrochemistry to fundamental physics to the study of chemical reactive intermediates. The limiting factor in developing a deeper understanding of many ion systems is the quality of the available laboratory spectra. Traditional techniques for …
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Tholins: A Gas Phase Computational Study of Methanimine and Related Species
… Scientists in the fields of astrobiology and astrochemistry believe that Titan’s current atmospheric conditions could resemble that of the primordial Earth, and as such is being studied to further our understanding of how life forms. While Titan’s atmosphere contains an abundance of organic …
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BINDING ENERGIES AND SOLVATION OF ORGANIC MOLECULAR IONS, REACTIONS OF TRANSITION METAL IONS WITH, AND PLASMA DISCHARGE IONIZATION OF MOLECULAR CLUSTERS
… molecular ions with relevance to astrochemistry. Ion mobility mass spectrometry and DFT computations were used to investigate how a second nitrogen in the pyrimidine ring will affect the formation of a covalent bond between the benzene radical cation and the neutral pyrimidine …
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Experiment and Modeling Combined Kinetic Study of Bottom-up Polycyclic Aromatic Hydrocarbon Formations
… of the knowledge learned from this thesis to astrochemistry. Overall, the studies here show a successful investigation of bottom-up PAH formation through experimental and theoretical approaches.
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On the Chemistry of Molecules Containing Silicon, Phosphorus, and Sulfur in the Interstellar Medium
… presents a collection of studies in Laboratory Astrochemistry aimed at providing new experimental data for astrochemical modeling and probing the fundamental chemistry underlying the phenomena investigated. The core of this thesis is the study of the reactivity in the gas phase of ions related …
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Spectroscopic study of photon, ion and electron stimulated molecular synthesis in astrophysical ices
… between radiation and matter pertinent to astrochemistry, e.g. ion, photon and electron processing of ices. <br></br><br></br> A detailed description of the design and construction of the new apparatus is given and the theory and instrumentation in the spectroscopic techniques used are …
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High-resolution infrared spectroscopy in pursuit of C60 and other astrochemical targets
… assignment, further increasing interest in the astrochemistry of C60. While these observations through emission spectroscopy have had a significant impact, emission spectroscopy is not an effective approach in cold regions of space with low ultraviolet flux - as such, obtaining a high-resolution …
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The nuclear spin dependence of the reaction of H3+ with H2 and the proposed spectroscopic investigation of HO2+
High-resolution spectroscopy of molecular ions has been proven to be a difficult endeavor. Generating significant quantities of the desired ions and discriminating ions from neutrals are among some of the many difficulties surrounding the spectroscopic studies of these species. Despite these …
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Following Carbon's Evolutionary Path: From Nucleosynthesis to the Solar System
Studies of carbon's evolutionary path have been conducted via millimeter and submillimeter observations of circumstellar envelopes (CSEs), planetary nebulae (PNe), molecular clouds and comets. The 12C/13C isotope ratio was measured in Galactic molecular clouds using the CN isotopologs. A gradient …
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Near-IR Spectroscopic Analysis of the Primary Volatile Composition of Long and Short-Period Comets
<p>"Comets are among the most well-preserved objects that formed in the protosolar nebula ∼4.5 Gyr ago. Hence, they are important for understanding various aspects of the formation, evolution, and habitability of the solar system. Multiple primary volatiles (molecules directly sublimating into the …
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Investigating the cosmic-ray ionization rate in the galactic interstellar medium through observations of H3+
Observations of H3+ in the Galactic diffuse interstellar medium (ISM) have led to various surprising results, including the conclusion that the cosmic-ray ionization rate (zeta_2) is about 1 order of magnitude larger than previously thought. The present survey expands the sample of diffuse cloud …
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High-resolution spectroscopic studies of carbon-containing species
High-resolution spectra of molecules and ions can provide valuable information fundamentally and astrochemically. From the fundamental side, high-resolution rovibrational spectroscopy allows molecular constants to be determined and provides evidence of theoretical assumptions. Work to this end was …
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Probing giant-planet forming zones around Solar-like stars with CO
Protoplanetary disks are dusty disks around young stars where planets are formed. The evolution and composition of protoplanetary disks determine the time, environments and materials available for planet formation. However fundamental properties of protoplanetary disks such as mass, composition, …
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Laboratory and Observational Studies of Transient Molecules at Microwave and Millimeter/Submillimeter Wavelengths
In this dissertation, techniques of high-resolution rotational spectroscopy have been used to measure the spectra of molecules in both laboratory and astronomical settings. In the laboratory, small metal-bearing molecules containing zinc, iron, nickel, titanium, yttrium, and scandium have been …
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Sensitive and high-precision rovibrational spectroscopy of molecular ions relevant to astronomical and quantum chemistry
High-precision spectroscopy of molecular ions has enabled new discoveries in astronomy and provided valuable benchmarks for ab initio calculations of molecular structure. Astronomers and theorists require accurate and precise laboratory measurements of rotational and rovibrational transition …
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Theoretical Prediction of Electronically Excited States and Vibrational Frequencies of Interstellar and Planetary Radicals, Anions, and Cations
In the search for molecular species in the interstellar medium and extraterrestrial planetary atmospheres, theoretical methods continue to be an invaluable tool to astronomically minded chemists. Using state-of-the art methods, this doctoral work characterizes the electronically excited states of …
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