Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Publication Type
Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Preparation Of Methanediamine (Ch2(Nh2)2)—A Precursor To Nucleobases In The Interstellar Medium, Joshua H. Marks, Jia Wang, Ryan C. Fortenberry, Ralf I. Kaiser
Preparation Of Methanediamine (Ch2(Nh2)2)—A Precursor To Nucleobases In The Interstellar Medium, Joshua H. Marks, Jia Wang, Ryan C. Fortenberry, Ralf I. Kaiser
Faculty and Student Publications
Although methanediamine (CH2(NH2)2) has historically been the subject of theoretical scrutiny, it has never been isolated to date. Here, we report the preparation of methanediamine (CH2(NH2)2)—the simplest diamine. Low-temperature interstellar analog ices composed of ammonia and methylamine were exposed to energetic electrons which act as proxies for secondary electrons produced in the track of galactic cosmic rays. These experimental conditions, which simulate the conditions within cold molecular clouds, . result in radical formation and initiate aminomethyl (ĊH2NH2) and amino (NH2) radical chemistry. Exploiting tunable photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS) to make isomer-specific assignments, methanediamine was identified in the gas …
The Spectral Features And Detectability Of Small, Cyclic Silicon Carbide Clusters, Christopher M. Sehring, C. Zachary Palmer, Brent R. Westbrook, Ryan C. Fortenberry
The Spectral Features And Detectability Of Small, Cyclic Silicon Carbide Clusters, Christopher M. Sehring, C. Zachary Palmer, Brent R. Westbrook, Ryan C. Fortenberry
Faculty and Student Publications
Rovibrational spectral data for several tetra-atomic silicon carbide clusters (TASCCs) are computed in this work using a CCSD(T)-F12b/cc-pCVTZ-F12 quartic force field. Accurate theoretical spectroscopic data may facilitate the observation of TASCCs in the interstellar medium which may lead to a more complete understanding of how the smallest silicon carbide (SiC) solids are formed. Such processes are essential for understanding SiC dust grain formation. Due to SiC dust prevalence in the interstellar medium, this may also shed light on subsequent planetary formation. Rhomboidal Si2C2 is shown here to have a notably intense (247 km mol−1) anharmonic vibrational frequency at 988.1 cm−1 …
Theoretical Spectra And Energetics For C-C3hc2h, L-C5h2, And Bipyramidal D3h C5h2, Alexandria G. Watrous, Brent R. Westbrook, Ryan C. Fortenberry
Theoretical Spectra And Energetics For C-C3hc2h, L-C5h2, And Bipyramidal D3h C5h2, Alexandria G. Watrous, Brent R. Westbrook, Ryan C. Fortenberry
Faculty and Student Publications
The recent astronomical detection of c-C3HC2H and l-C5H2 has led to increased interest in C5H2 isomers and their relative stability. The present work provides the first complete list of anharmonic vibrational spectral data with infrared intensities for three such isomers as well as including the first set of rotational data for the bipyramidal C5H2 isomer allowing for these molecules to serve as potential tracers of interstellar carbon. All three isomers have fundamental vibrational frequencies with at least one notably intense fundamental frequency. The l-C5H2 isomer has, by far, the highest intensities out of the three isomers at 2076.3 cm−1 (738 …
Computational Investigations Into Astrochemical Inorganic Oxides, Ammonia Borane, And Genetic Algorithms, E. Michael Valencia
Computational Investigations Into Astrochemical Inorganic Oxides, Ammonia Borane, And Genetic Algorithms, E. Michael Valencia
Honors Theses
The formulations of quantum mechanics in the early 1900s were exciting theoretical discoveries, but were not practical to apply until the advent of computers and the subsequent computational methods in 1951. With the introduction of tractable simplifications, procedures such as Hartree-Fock allowed for determination of properties of non-trivial systems. Presently, huge leads of computational power have allowed for extremely precise, quantitative work that can be applied to the human body, synthesis, or even astrochemical processes. This thesis presents works concerning 1) the history of quantum mechanics; 2) a brief primer on computational chemistry and its methods; 3) inorganic oxides in …
Spectral Signatures Of Hydrogen Thioperoxide (Hosh) And Hydrogen Persulfide (Hssh): Possible Molecular Sulfur Sinks In The Dense Ism, Charles Z. Palmer, Ryan C. Fortenberry, Joseph S. Francisco
Spectral Signatures Of Hydrogen Thioperoxide (Hosh) And Hydrogen Persulfide (Hssh): Possible Molecular Sulfur Sinks In The Dense Ism, Charles Z. Palmer, Ryan C. Fortenberry, Joseph S. Francisco
Faculty and Student Publications
For decades, sulfur has remained underdetected in molecular form within the dense interstellar medium (ISM), and somewhere a molecular sulfur sink exists where it may be hiding. With the discovery of hydrogen peroxide (HOOH) in the ISM in 2011, a natural starting point may be found in sulfur-bearing analogs that are chemically similar to HOOH: hydrogen thioperoxide (HOSH) and hydrogen persulfide (HSSH). The present theoretical study couples the accuracy in the anharmonic fundamental vibrational frequencies from the explicitly correlated coupled cluster theory with the accurate rotational constants provided by canonical high-level coupled cluster theory to produce rovibrational spectra for use …
Valence-, Dipole-And Quadropole-Bound Electronically Excited States Of Closed-Shell Anions Formed By Deprotonation Of Cyano-And Ethynyl-Disubstituted Polycyclic Aromatic Hydrocarbons, Marie E. Strauss, Taylor J. Santaloci, Ryan C. Fortenberry
Valence-, Dipole-And Quadropole-Bound Electronically Excited States Of Closed-Shell Anions Formed By Deprotonation Of Cyano-And Ethynyl-Disubstituted Polycyclic Aromatic Hydrocarbons, Marie E. Strauss, Taylor J. Santaloci, Ryan C. Fortenberry
Faculty and Student Publications
Dicyano-functionalized benzene and naphthalene anion derivatives exhibit a relatively rich population of electronically excited states in stark contrast to many assumptions regarding the photophysics of anions in general. The present work has quantum chemically analyzed the potential electronically excited states of closed-shell anions created by replacing hydrogen atoms with valence-bound lone pairs in benzene and naphthalene difunctionalized with combinations of-CN and-C2H. Dicyanobenzene anion derivatives can exhibit dipole-bound excited states as long as the cyano groups are not in para position to one another. This also extends to cyanoethynylbenzene anions as well as deprotonated dicyano-and cyanoethynylnaphthalene anion derivatives. Diethynyl functionalization is …
Synthesis Of Methanediol [Ch2(Oh)2]: The Simplest Geminal Diol, Cheng Zhu, N. Fabian Kleimeier, Andrew M. Turner, Santosh K. Singh, Ryan C. Fortenberry, Ralf I. Kaiser
Synthesis Of Methanediol [Ch2(Oh)2]: The Simplest Geminal Diol, Cheng Zhu, N. Fabian Kleimeier, Andrew M. Turner, Santosh K. Singh, Ryan C. Fortenberry, Ralf I. Kaiser
Faculty and Student Publications
Geminal diols—organic molecules carrying two hydroxyl groups at the same carbon atom—have been recognized as key reactive intermediates by the physical (organic) chemistry and atmospheric science communities as fundamental transients in the aerosol cycle and in the atmospheric ozonolysis reaction sequence. Anticipating short lifetimes and their tendency to fragment to water plus the aldehyde or ketone, free geminal diols represent one of the most elusive classes of organic reactive intermediates. Here, we afford an exceptional glance into the preparation of the previously elusive methanediol [CH2(OH)2] transient—the simplest geminal diol—via energetic processing of low-temperature methanol–oxygen ices. Methanediol was identified in the …
Computational Investigation Of Stellar Cooling, Noble Gas Nucleation, And Organic Molecular Spectra, Jax Dallas
Computational Investigation Of Stellar Cooling, Noble Gas Nucleation, And Organic Molecular Spectra, Jax Dallas
Honors Theses
Since the advent and optimization of the Hartree-Fock method, quantum chemistry has been utilized to investigate systems operating on timeframes and environments traditionally unavailable to bench-top chemistry. As computational methods have grown more robust and less time consuming, quantum chemistry has been utilized to investigate a range of fields, including the steadily growing discipline of computational astrochemistry. Through the lens of computational astrochemistry, chemistry that occurred billions of years ago can be explored with equal clarity to that which is currently happening in the cosmos. The work presented throughout this thesis is a series of investigations into different timeframes of …
Pathways To Detection Of Strongly-Bound Inorganic Species: The Vibrational And Rotational Spectral Data Of Alh2oh, Hmgoh, Alh2nh2, And Hmgnh2, Alexandria G. Watrous, Megan C. Davis, Ryan C. Fortenberry
Pathways To Detection Of Strongly-Bound Inorganic Species: The Vibrational And Rotational Spectral Data Of Alh2oh, Hmgoh, Alh2nh2, And Hmgnh2, Alexandria G. Watrous, Megan C. Davis, Ryan C. Fortenberry
Faculty and Student Publications
Small, inorganic hydrides are likely hiding in plain sight, waiting to be detected toward various astronomical objects. AlH2OH can form in the gas phase via a downhill pathway, and the present, high-level quantum chemical study shows that this molecule exhibits bright infrared features for anharmonic fundamentals in regions above and below that associated with polycyclic aromatic hydrocarbons. AlH2OH along with HMgOH, HMgNH2, and AlH2NH2 are also polar with AlH2OH having a 1.22 D dipole moment. AlH2OH and likely HMgOH have nearly unhindered motion of the hydroxyl group but are still strongly bonded. This could assist in gas phase synthesis, where …
Electronically Excited States Of Closed-Shell, Cyano-Functionalized Polycyclic Aromatic Hydrocarbon Anions, Taylor J. Santaloci, Ryan C. Fortenberry
Electronically Excited States Of Closed-Shell, Cyano-Functionalized Polycyclic Aromatic Hydrocarbon Anions, Taylor J. Santaloci, Ryan C. Fortenberry
Faculty and Student Publications
Few anions exhibit electronically excited states, and, if they do, the one or two possible excitations typically transpire beyond the visible spectrum into the near-infrared. These few, red-shifted electronic absorption features make anions tantalizing candidates as carriers of the diffuse interstellar bands (DIBs), a series of mostly unknown, astronomically ubiquitous absorption features documented for over a century. The recent interstellar detection of benzonitrile implies that cyano-functionalized polycyclic aromatic hydrocarbon (PAH) anions may be present in space. The presently reported quantum chemical work explores the electronic properties of deprotonated benzene, naphthalene, and anthracene anions functionalized with a single cyano group. Both …
Anharmonic Vibrational Frequencies And Spectroscopic Constants For The Detection Of Ethynol In Space, Jax D. Dallas, Brent R. Westbrook, Ryan C. Fortenberry
Anharmonic Vibrational Frequencies And Spectroscopic Constants For The Detection Of Ethynol In Space, Jax D. Dallas, Brent R. Westbrook, Ryan C. Fortenberry
Faculty and Student Publications
The ethynol (HCCOH) molecule has recently been shown to be present in simulated astrochemical ices possibly linking it to molecular building blocks for interstellar complex organic molecules like amino acids. The proposed reaction mechanism suggests the simultaneous formation of both ketene and ethynol from mixed carbon monoxide/water ice in simulated interstellar conditions. Rigorous anharmonic spectral data within both the IR and microwave regions are needed for possible detection of ethynol in the interstellar medium. This study provides the first such data for this molecule from high-level quantum chemical computations where experiment is currently lacking. Ethynol has a (Formula presented.) comparable …
Untangling The Formation Of Methoxymethanol (Ch3Och2Oh) And Dimethyl Peroxide (Ch3Ooch3) In Star-Forming Regions, Cheng Zhu, Robert Frigge, Alexandre Bergantini, Ryan C. Fortenberry, Ralf I. Kaiser
Untangling The Formation Of Methoxymethanol (Ch3Och2Oh) And Dimethyl Peroxide (Ch3Ooch3) In Star-Forming Regions, Cheng Zhu, Robert Frigge, Alexandre Bergantini, Ryan C. Fortenberry, Ralf I. Kaiser
Faculty and Student Publications
© 2019. The American Astronomical Society. All rights reserved.. Methoxymethanol (CH3OCH2OH) was recently detected toward the MM1 core in the high-mass star-forming region NGC 6334I. However, the underlying formation mechanisms of this complex organic molecule (COM) as well as its structural isomers ethylene glycol (HOCH2CH2OH) and the hitherto unobserved dimethyl peroxide (CH3OOCH3) are still elusive. Here, we report the very first confirmed synthesis of dimethyl peroxide - at various deuteration levels within interstellar analogous ices of D3-methanol (CD3OH) exposed to ionizing radiation at ultralow temperatures of 5 K. The discrimination of specific isomers is achieved by exploiting reflectron time-of-flight mass …