Tautomeric forms of adenine: Vertical ionization energies and Dyson orbitals

Singh, R. V.; Ortiz, J. V.; Mishra, Manoj K.

doi:10.1002/qua.22363

Cited by 31 publications

(23 citation statements)

References 63 publications

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“…Adenine occurs in a number of tautomeric forms [21,22]. Touboul et al [23] have performed VUV photoionization of gas phase adenine and have made a comparison between oven and aerosol vaporization showing that jet-cooling of vaporized adenine efficiently leads to the predominance of the most stable 9H-amino tautomer (ade-n9) in the beam.…”

Section: Methodsmentioning

confidence: 99%

Electron impact fragmentation of adenine: partial ionization cross sections for positive fragments

2015

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Abstract. Using computer-controlled data acquisition we have measured mass spectra of positive ions for electron impact on adenine, with electron energies up to 100 eV. Ion yield curves for 50 ions have been obtained and normalized by comparing their sum to the average of calculated total ionization cross sections. Appearance energies have been determined for 37 ions; for 20 ions for the first time. All appearance energies are consistent with the fragmentation pathways identified in the literature. Second onset energies have been determined for 12 fragment ions (for 11 ions for the first time), indicating the occurrence of more than one fragmentation process e.g. for 39 u (C2HN + ) and 70 u (C2H4N + 3 ). Matching ion yield shapes (118-120 u, 107-108 u, 91-92 u, and 54-56 u) provide new evidence supporting closely related fragmentation pathways and are attributed to hydrogen rearrangement immediately preceding the fragmentation. We present the first measurement of the ion yield curve of the doubly charged parent ion (67.5 u), with an appearance energy of 23.5 ± 1.0 eV.

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Section: Methodsmentioning

confidence: 99%

Electron impact fragmentation of adenine: partial ionization cross sections for positive fragments

2015

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“…Many applications of ab initio electron propagator methods to neutral and anionic carbon clusters, fullerenes, porphyrins, phthalocyanines, nucleic acid fragments, polycyclic aromatic hydrocarbons, organometallics, and other organic compounds have been reported and reviewed recently by the author and his collaborators 61–93. In collaboration with Martínez and coworkers94–102 and Zein103,104 photoelectron spectra of metal‐oxide clusters anions have been assigned and patterns of electronic structure and reactivity have been analyzed with the aid of Dyson orbitals.…”

Section: Survey Of Recent Applicationsmentioning

confidence: 99%

“…Mishra and coworkers have applied several electron propagator approximations to the study of nitrogen‐rich anionic rings,144,145 interactions between functional groups in cyclic compounds146–148 and tautomers of nucleic‐acid bases 149…”

Section: Survey Of Recent Applicationsmentioning

confidence: 99%

Electron propagator theory: an approach to prediction and interpretation in quantum chemistry

Ortiz

2012

WIREs Comput Mol Sci

191

194

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Electron propagator theory provides a practical means of calculating electron binding energies, Dyson orbitals, and ground‐state properties from first principles. This approach to ab initio electronic structure theory also facilitates the interpretation of its quantitative predictions in terms of concepts that closely resemble those of one‐electron theories. An explanation of the physical meaning of the electron propagator's poles and residues is followed by a discussion of its couplings to more complicated propagators. These relationships are exploited in superoperator theory and lead to a compact form of the electron propagator that is derived by matrix partitioning. Expressions for reference‐state properties, relationships to the extended Koopmans's theorem technique for evaluating electron binding energies, and connections between Dyson orbitals and transition probabilities follow from this discussion. The inverse form of the Dyson equation for the electron propagator leads to a strategy for obtaining electron binding energies and Dyson orbitals that generalizes the Hartree–Fock equations through the introduction of the self‐energy operator. All relaxation and correlation effects reside in this operator, which has an energy‐dependent, nonlocal form that is systematically improvable. Perturbative arguments produce several, convenient (e.g. partial third order, outer valence Green's function, and second‐order, transition‐operator) approximations for the evaluation of valence ionization energies, electron affinities, and core ionization energies. Renormalized approaches based on Hartree–Fock or approximate Brueckner orbitals are employed when correlation effects become qualitatively important. Reference‐state total energies based on contour integrals in the complex plane and gradients of electron binding energies enable exploration of final‐state potential energy surfaces. © 2012 John Wiley & Sons, Ltd. This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods

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“…We have shown previously, that the EPT decouplings provide new insights with accurate resolution of PES for large organic molecules. [30][31][32] It is our purpose in this paper to apply various decouplings of the one electron propagator on ethynylthiophenes, using sufficiently large basis sets to provide dependable results which can be utilized for accurate understanding of photoelectron data that are available for this important class of monomers with potential for multifaceted practical applications.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure analysis and vertical ionization energies of thiophene and ethynylthiophenes

Singh

Mishra

2009

J Chem Sci

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Results from different decouplings of the electron propagator theory using MP2/6-311g (2df, 2p) and MP2/6-311++g (2df, 2p) optimized geometries have been performed to investigate first eight vertical ionization energies and the corresponding Dyson orbitals. The results computed are in good agreement with experimental ionization energies and help clear the ambiguities of experimental photoelectron spectrum (PES) assignments. Detailed examination of the π-orbital density distribution of Dyson orbitals provides clarity in PES assignments and new insights about the topology of ring π and ethynyl π c-c electron density distribution which may be tapped for improved nonlinear optical/electrochemical response from the thiophenic conjugated polymers.

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Tautomeric forms of adenine: Vertical ionization energies and Dyson orbitals

Cited by 31 publications

References 63 publications

Electron impact fragmentation of adenine: partial ionization cross sections for positive fragments

Electron impact fragmentation of adenine: partial ionization cross sections for positive fragments

Electron propagator theory: an approach to prediction and interpretation in quantum chemistry

Electronic structure analysis and vertical ionization energies of thiophene and ethynylthiophenes

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