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Articles 1 - 8 of 8
Full-Text Articles in Chemistry
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 …
State-To-State Rate Coefficients For Hcs+In Rotationally Inelastic Collisions With H2at Low Temperatures, Otoniel Denis-Alpizar, Ernesto Quintas-Sánchez, Richard Dawes
State-To-State Rate Coefficients For Hcs+In Rotationally Inelastic Collisions With H2at Low Temperatures, Otoniel Denis-Alpizar, Ernesto Quintas-Sánchez, Richard Dawes
Chemistry Faculty Research & Creative Works
HCS+ ions have been detected in several regions of the interstellar medium (ISM), but an accurate determination of the chemical-physical conditions in the molecular clouds where this molecule is observed requires detailed knowledge of the collisional rate coefficients with the most common colliders in those environments. In this work, we study the dynamics of rotationally inelastic collisions of HCS+ + H2 at low temperature, and report, for the first time, a set of rate coefficients for this system. We used a recently developed potential energy surface for the HCS+-H2 van der Waals complex and …
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 …