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"Estudos sintéticos e teóricos sobre anulenos e baquenolidas" ; Synthetical and Theoretical Studies about Annulenes and Bakkenolides

Oliveira, Kleber Thiago de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/08/2006 PT
Relevância na Pesquisa
45.83%
Neste trabalho foram desenvolvidos alguns estudos que tiveram como objetivo principal a utilização de reações de cicloadição como a Reação de Diels–Alder e a Cicloadição do tipo [6+4] na síntese de anulenos e baquenolidas. Na primeira parte (Parte A) são apresentadas algumas abordagens com o objetivo de produzir sistemas do tipo biciclo[6.2.1]undecano (42), similares a sistemas existentes em produtos naturais e que são precursores diretos do 1,4–metano[10]anuleno (41), uma estrutura hipotética, cuja síntese ainda não foi descrita. Os melhores resultados foram obtidos através de uma cicloadição [6+4] entre o ciclopentadieno 43 e a tropona 139 o que forneceu 140. Este produto guarda grande semelhança estrutural com o anuleno 41. Para efetuar o rompimento da ponte carbonílica, o melhor método que encontramos consistiu em transformar a cetona 140 em oxima, depois em lactama através de um rearranjo de Beckmann, transformação na forma tosilada e redução com LiAlH4. O álcool primário de 171 pôde ser eliminado com relativa facilidade, mas o grupo NHTs mostrou–se extremamente resistente à alquilação exaustiva/eliminação; apenas quando utilizamos sal de oxônio tivemos evidências de formação de carbocátion. No entanto...

"Estudo experimental e teórico de compostos de bases de Schiff com cobre (II)"; "Experimental and theoretical studies on copper(II) Schiff Bases"

Tozzo, Érica
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/09/2006 PT
Relevância na Pesquisa
55.75%
Neste trabalho inicialmente foi feita uma breve apresentação sobre a utilização de compostos de bases de Schiff e Cobre(II) como catalisadores na reação de oxidação de sulfetos. Foi feita a determinação das estruturas cristalinas dos compostos: N,N'-bis(3-etoxisalicilideno)-(1,2etileno- diamina) Cu(II), sistema cristalino ortorrômbico grupo espacial Pbcn a = 7.639(5); b= 12.760(5); c= 19.733(5)Å; V = 1923.4(15) (3)Å3; Dcalc = 1.505 Mg/m3; MM = 435.96; e m = 1.170 mm-1, N,N'-bis (4-dietilaminasalicilideno) - (1,2etilenodiamina) Cu(II), sistema monoclínico, C2/c, a = 19.571(2); b=9.8514(2)=; c=12.4552(4) Å; Beta = 93.705(9)o; V =2396.4(5) Å3; Dcalc=1.358 Mg.m-3; MM= 490.10; e m = 0.944 mm-1, N,N'-bis(3-metoxisalicilideno)-(1,2etilenodiamina)Cu(II), sistema ortorrômbico, Pna21, a = 7.5140(6); b= 9.2629(9); c= 24.721(3)Å; V =1720.6(3) Å3; Dcalc = 1.575 Mg,m-1; MM = 407.91; e m = 1.302 mm1 e (SALAHE)Cu(II), monoclínico, P21/C, a = 18.3216(2) Å; b=4.804(3) Å; c=19.801(2)Å; Beta = 98.908(6)o; V =2396.4(5) Å3; Dcalc=1.358 Mg.m-3; MM= 490.10; e m = 0.944 mm-1. Os cálculos teóricos para as quatro moléculas foram efetuados partindo-se das coordenadas atômicas cristalográficas. Foram modeladas, para posterior estudo teórico...

Estudos teóricos sobre colisões mediadas por fótons e gases quânticos bosônicos rarefeitos; Theoretical studies on cold atomic collisions mediated by photons and low-density quantum bosonic gases

Montalvão, Rinaldo Wander
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/04/2001 PT
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45.66%
Neste trabalho elaboramos estudos teóricos sobre colisões frias mediadas por fótons em armadilhas magnéto-ópticas. Para isto implementamos algorítimos numéricos de alto desempenho para o cálculo das formas de linha do espectro de fotoassociação do 88Sr. O principal algorítimo utilizado foi o de Numerov renormalizado. Também foram implementados sistemas de construção dos elementos da matriz hamiltoniana para estudos de colisões atômicas levando em consideração a estrutura fina dos potenciais de interação. Por último introduzimos o método de Monte Carlo de Integrais sobre Trajetórias como ferramenta para o estudo da termodinâmica do condensado de Bose-Einstein em armadilhas 2D considerando a interação entre os átomos; In this work we present theoretical studies of cold collisions mediated by photons in magneto-optical traps. We have implemented high-performance numerical algorithms to calculate the photoassociation spectral line shapes of 88Sr. We have mainly utilized the renormalized Numerov algorithm. We have also implemented schemes to write down the Hamiltonian matrix elements to study atomic collisions taking into account the fine structure of the interaction potentials. Finally, we have introduced the Path Integral Monte Carlo method as a tool for studying the thermodynamics of the Bose-Einstein condensate in two-dimensional traps...

Theoretical Studies of Proton-Coupled Electron Transfer: Models and Concepts Relevant to Bioenergetics

Hammes-Schiffer, Sharon; Hatcher, Elizabeth; Ishikita, Hiroshi; Skone, Jonathan H.; Soudackov, Alexander V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/02/2008 EN
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45.86%
Theoretical studies of proton-coupled electron transfer (PCET) reactions for model systems provide insight into fundamental concepts relevant to bioenergetics. A dynamical theoretical formulation for vibronically nonadiabatic PCET reactions has been developed. This theory enables the calculation of rates and kinetic isotope effects, as well as the pH and temperature dependences, of PCET reactions. Methods for calculating the vibronic couplings for PCET systems have also been developed and implemented. These theoretical approaches have been applied to a wide range of PCET reactions, including tyrosyl radical generation in a tyrosine-bound rhenium polypyridyl complex, phenoxyl/phenol and benzyl/toluene self-exchange reactions, and hydrogen abstraction catalyzed by the enzyme lipoxygenase. These applications have elucidated some of the key underlying physical principles of PCET reactions. The tools and concepts derived from these theoretical studies provide the foundation for future theoretical studies of PCET in more complex bioenergetic systems such as Photosystem II.

Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Diethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

Fales, B. S.; Fujamade, N. O.; Nei, Y.-w.; Oomens, J.; Rodgers, M. T.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
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45.76%
The gas-phase structures of deprotonated, protonated, and sodium-cationized complexes of diethyl phosphate (DEP) including [DEP − H]−, [DEP + H]+, [DEP + Na]+, and [DEP − H + 2Na]+ are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) with an electrospray ionization (ESI) source, and theoretical electronic structure calculations. Measured IRMPD spectra are compared to linear IR spectra calculated at the B3LYP/6-31G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral complexes are also performed. These experiments and calculations suggest that specific geometric changes occur upon the binding of protons and/or sodium cations, including changes correlating to nucleic acid backbone geometry, specifically P–O bond lengths and ∠OPO bond angles. Information from these observations may be used to gain insight into the structures of more complex systems, such as nucleotides and solvated nucleic acids.

Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review

Kleinstreuer, Clement; Feng, Yu
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 01/07/2011 EN
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Correction to Kleinstreuer C, Feng Y: Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review. Nanoscale Research Letters 2011, 6:229.

Synthesis, Characterization, and Theoretical Studies of Metal Complexes Derived from the Chiral Tripyridyldiamine Ligand Bn-CDPy3

Abouelatta, Ahmed I.; Sonk, Jason A.; Hammoud, Mirvat M.; Zurcher, Danielle M.; McKamie, Joshua J.; Schlegel, H. Bernhard; Kodanko, Jeremy J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 07/06/2010 EN
Relevância na Pesquisa
45.76%
Synthesis and characterization of metal complexes of the chiral tripyridyldiamine ligand Bn-CDPy3 (1), derived from trans-1,2-diaminocyclohexane, are described, along with theoretical studies that support the experimental data. These studies confirm that a single coordination geometry, out of five possible, is favored for octahedral complexes of the type [M(Bn-CDPy3)Cl], where M equals Co(III), Fe(II), and Zn(II). A combination of X-ray crystallographic and NMR spectroscopic methods was used to define the structures of the complexes [Co(Bn-CDPy3)Cl]Cl2 (5), [Fe(Bn-CDPy3)Cl]X (X = FeCl4, Cl, ClO4, 6–8), and [Zn(Bn-CDPy3)Cl]2ZnCl4 (9) in the solid state and in solution. Experimental and theoretical data indicate that the most stable coordination geometry for all complexes possesses the Cl group trans to a basic amine donor and three pyridyl donors adopting the mer geometry, with two pyridyl N-donors adopting a coplanar geometry with respect to the M–Cl bond and the third pyridyl donor perpendicular to that axis. Calculations indicate that the ability to favor a single geometry is born from the chiral ligand, which prefers to be in a single conformation in metal complexes due to steric interactions and electronic factors. Calculated structures of the complexes were used to locate key interactions among the various diastereomeric complexes that are proposed to create an energetic preference for the coordination geometry observed in the metal complexes of 1.

Storytelling on the margins : a theoretical framework for imagining a fashion innovation center in Tuscany; Theoretical framework for imagining a fashion innovation center in Tuscany

Mills, Alexa (Alexa Timeaus)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 68 leaves
ENG
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45.74%
The importance of the margin has long been deemed important in creative processes. At both the level of the individual and the level of the city, research shows that creativity tends to flourish on the philosophical and physical outskirts of society. This thesis expands upon this theory by looking at a second, less documented trend of creative "edge" institutions: their deliberate use of storytelling for growth and idea development. This thesis examines these trends through three case studies, chosen to illuminate the particular case of Castel Pulci, a declining, vacant villa located ten miles outside of Florence, Italy, which the Italian government has slotted for physical and programmatic renovations to become a center for innovation and business in the fashion industry. The findings indicate that, in addition to exploiting their "edge" positions, innovative institutions pay constant, conscious, and deliberate attention to the role of narrative in their operations. Whether understanding objects, imagining the future, bringing a community together, or selling a product, the research in these case studies suggest that the use of storytelling is pivotal for innovative "edge" institutions.; by Alexa Mills.; Thesis (M.C.P.)--Massachusetts Institute of Technology...

Understanding the Origin of Selectivity in the Asymmetric Lithiation Reaction of N-Heterocycles: A Theoretical Study

Taban, Keivan
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
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45.72%
The natural abundance of the N-heterocycle containing compounds has pushed the synthetic community toward the invention of new synthetic methods that result in the structural diversity of N-heterocycles. Among this, is the efficient and highly selective diamine mediated asymmetric lithiation process. Amongst the diamine chiral ligands, (-)-sparterine, which is a naturally occurring alkaloid proved to be an efficient one. Many successful, good yielding and highly selective lithiation reactions have been accomplished with the mediation by this chiral diamine base. Although, there are some examples of experimental and theoretical mechanistic studies in the literature, there is a lack of detailed understanding as to how it exactly induces the chirality. In this thesis is described a systematic investigation of how (-)-sparteine influences the stereoselectivity in the course of asymmetric lithiation reaction. This led us to the establishment of the function of A-ring’s β-CH2 effect and D-ring effect. Consequently, the importance of the A-ring and D-ring portions of (-)-sparteine in the stereoselectivity is unraveled. Another part of this thesis deals with the asymmetric lithiation of BF3-activated N,N- dimethylaminoferrocene in the presence of (1R...

Theoretical studies for ozonide formation during the ozonolysis of bicyclic endoperoxides

Cain, N.; Hixson, J.; Taylor, D.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
45.68%
Theoretical investigations on the treatment of bicyclic endoperoxides (1,2-dioxines) with ozone at the HF/6-31G*, MP2/6-31G*or 6-311G*, and DFT(B3LYP)/6-31G*levels of theory indicate that the estimated activation energies for formation of the possible endo-endo, endo-exo, exo-endo, or exo-exo transition states along with the formation of the primary ozonides and product ozonides are very sensitive to effects of electron correlation and basis set. This study suggests that MP2/6-311G*is the best level of theory for evaluating such systems. At the MP2/6-311G*level of theory it was found that the transition state for primary ozonide formation was lowest in energy when ozone approaches in an endo facial fashion with a further 3kJmol-1 stabilisation seen when the central oxygen within the primary ozonide protrudes outwards (exo) as opposed to inwards (endo). The product ozonides are predicted to be more stable than the combined starting materials by some 380-580kJmol-1 depending on the level of theory, clearly highlighting the substantive exothermic nature of this type of ozonolysis reaction.; Nicole M. Cain, Josh L. Hixson, and Dennis K. Taylor

Theoretical studies of molecular machines

Akimov, Alexey V.
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: 206 p.; application/pdf
ENG
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45.82%
Only volume 2 has been digitized.; Molecular machines are essential components of living organisms. They are highly efficient and robust, much more than their macroscopic analogs. This stimulated growing interest in construction of artificial molecular machines with a set of functions which may be controlled in a specific way. Such man-made molecular complexes are designed as the building blocks for future nanotechnological devices. During the last decades many new molecular machines have been synthesized and characterized by various experimental techniques. This significantly increased our knowledge about systems of such kind and their functioning. However, there are only a few real applications of molecular machines. This is because the fundamental principles of operation of such single-molecule systems are not well understood. Existing theoretical studies, although very helpful, are still very sparse. This is because the molecular machines are very complex systems, comprising up to thousands atoms. Thus the progress in our understanding of nanoscale materials is tightly related to development of efficient computational and theoretical methodologies. In this work we studied two large classes of molecular machines: surface-moving nanocars and molecular rotors/motors...

Clients' narratives in psychotherapy and therapist's theoretical orientation : an exploratory analysis of Gloria's narratives with Rogers, Ellis and Perls

Moreira, Paulo; Gonçalves, Óscar F.; Matias, Carla
Fonte: International Institute for the Advanced Studies of Psychotherapy and Applied Mental Health Publicador: International Institute for the Advanced Studies of Psychotherapy and Applied Mental Health
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
45.78%
The therapist’s theoretical orientation has been shown to impact the psychotherapy process. However, less is known about the extent to which the therapist’s orientation may impact clients’ narratives. This exploratory study analysed clients’ narrative production in psychoptherapy, when interacting with different therapists. The data consisted of transcripts of Shostrom’s videotaped therapy sessions between the client Gloria and the therapists Carl Rogers, Fritz Perls and Albert Ellis. Gloria’s narratives were analyzed in terms of narrative dimensions: structural coherence, process complexity and content multiplicity. Gloria’s narratives where characterised by higher levels of stuctural coherence, process complexity and content multiplicity when interacting with Carl Rogers. This exploratory study identified the tendency of clients’ narrative production in psychotherapy vary accordingly to the therapist theoretical orientation. Future studies (using more robust methodologies) that contribute to clarify the impact of the therapist theoretical orientation on narrative co-construction in psychotherapy settings are needed.

The design of a new truncated and engineered alpha1-antitrypsin based on theoretical studies: an antiprotease therapeutics for pulmonary diseases

Pirooznia, Nazanin; Hasannia, Sadegh; Arab, Seyed Shahriar; Lotfi, Abbas Sahebghadam; Ghanei, Mostafa; Shali, Abbas
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 24/05/2013 EN
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45.66%
Alpha 1- antitrypsin (α1AT) a 54 kDa glycoprotein is a protease inhibitor. In the absence of α1AT, elastase released by lung macrophages, was not inhibited and lead to elastin breakdown and pulmonary problems such as emphysema or COPD. α1AT has three site of N-glycosylation and a characteristic reactive central loop (RCL). As small-scale medicines are preferred for pulmonary drug delivery, in this study α1ATs (1, 2, 3, 4 and 5) were engineered and shortened from the N-terminal region. In order to investigate the effect of different mutations and the deletion of 46 amino acids theoretical studies were performed. Homology modeling was performed to generate the 3D structure of α1ATs. The 10 ns Molecular Dynamic (MD) simulations were carried out to refine the models. Results from MD and protein docking showed that α1AT2 has the highest binding affinity for neutrophil elastase, provided the basis for the experimental phase in which sequences from the five α1AT constructs were inserted into the expression vector pGAPZα and expressed in the yeast Pichia pastoris. Although, the α1AT2 construct has the highest inhibitory activity even more that the native construct (α1AT5), results indicated the presence of protease inhibitory function of all the proteins' construct against elastase.

Enantioselective synthesis of beta-Amino acids. 12. experimental and theoretical study of the diastereoselectivity of alkylation of the dianion of N',N'-Bis(alpha-phenylethyl)-N -carbobenzyloxypropionamide

Gutiérrez-García,Víctor Manuel; Reyes-Rangel,Gloria; Muñoz-Muñiz,Omar; Juaristi,Eusebio
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2001 EN
Relevância na Pesquisa
55.76%
Achiral, inexpensive beta-alanine was converted into the title chiral amide 1 in 53% overall yield. C-Alkylation of (R,R)-1 required formation of its dianion derivative, (R,R)-1-Li2, which was best achieved by direct metallation with two equivalents of n-BuLi in THF solution and at -78°C. Treatment of (R,R)-1-Li2 with various alkyl halides afforded the monoalkylated products 3-6 in 24-85% yield and 65-86% diastereoselectivity. The effect of LiCl additive or HMPA co-solvent on the diastereoselectivity of the alkylation reaction was essentially negligible, although reaction yields generally improved. Chemical correlation of the major diastereomer from the methylation reaction with (S)-alpha-methyl-beta-alanine shows that addition of the electrophile takes place preferentially on the enolate's Si face. This conclusion is also supported by molecular modelling studies (ab initio HF/3-21G), which indicate that the conformation of lowest energy for (R,R)-1-Li2 presents a more sterically hindered Re face of the enolate. The theoretical studies also provided useful insight into the importance of hydrogen bonding and attractive p-p interactions in (R,R)-1. Furthermore, the calculations predict a determining role for N-Li-O chelation in (R...

Theoretical Studies of Superconductor-Insulator Transitions

Loh, Yen Lee; Trivedi, Nandini
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/09/2013
Relevância na Pesquisa
45.66%
In this article we study superconductor-insulator transitions within the general framework of an attractive Hubbard model. This is a well-defined model of s-wave superconductivity which permits different tuning parameters (disorder and field). Furthermore, it allows a comparison of various analytical and computational approaches in order to gain a complete understanding of the various effects of amplitude and phase fluctuations. We present a systematic pedagogical approach, aiming to equip the lay reader with enough apparatus to be able to understand the numerical calculations, reproduce some of the simpler results, and be able to tackle future problems related to inhomogeneous phases. We go into considerable detail on mean-field theory (MFT) and the Bogoliubov-de Gennes (BdG) approach, as these are a first line of attack which can capture much of the physics, but we also outline cases where this fails to capture phase fluctuations and more sophisticated Quantum Monte Carlo (QMC) calculations are necessary. We discuss the behavior of many observables, including densities of states, superfluid stiffness, and dynamical conductivity, for the disorder-tuned superconductor-insulator transition. We also discuss SITs tuned by parallel magnetic field...

Theoretical studies of Q1D organic conductors:a personal view

Celebonovic, V.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/12/2004
Relevância na Pesquisa
45.66%
This is a review of some aspects of theoretical studies of the Bechgaard salts,which also retraces the evolution of the author's interest in the field.It discusses the calculation of the condutivity,attempts at gaining some knowledge on the EOS and thermal properties of these materials,as well as some ideas on the possible future developement of the field.; Comment: 21 pages,plain LaTeX

Theoretical studies of photoexcitation and ionization in H_2O

Diercksen, G. H. F.; Kraemer, W. P.; Rescigno, T. N.; Bender, C. F.; McKoy, B. V.; Langhoff, S. R.; Langhoff, P. W.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 15/01/1982
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45.74%
Theoretical studies are reported of the complete dipole excitation and ionization spectrum in H_2O employing Franck–Condon and static‐exchange approximations. Large Cartesian Gaussian basis sets are used to represent the required discrete and continuum electronic eigenfunctions at the ground‐state equilibrium geometry, and previously devised moment‐theory techniques are employed in constructing the continuum oscillator‐strength densities from the calculated spectra. Detailed comparisons are made of the calculated excitation and ionization profiles with recent experimental photoabsorption studies and corresponding spectral assignments, electron impact–excitation cross sections, and dipole (e, 2e)/(e, e+ion) and synchrotron‐radiation studies of partial‐channel photoionization cross sections. The various calculated excitation series in the outer‐valence (1b(^−1)_1, 3a(^−1)_1, 1b(^−1)_2) region are found to include contributions from valence‐like 2b_2 (σ*) and 4a_1(γ*) virtual orbitals, as well as appropriate nsa_1, npa_1, nda_1, npb_1, npb_2, ndb_1, ndb_2, and nda_2 Rydberg states. Transition energies and intensities in the ∼7 to 19 eV interval obtained from the present studies are seen to be in excellent agreement with the measured photoabsorption cross section...

Photoexcitation and ionization in carbon dioxide: Theoretical studies in the separated-channel static-exchange approximation

Padial, N.; Csanak, G.; McKoy, B. V.; Langhoff, P. W.
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /01/1981
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45.72%
Theoretical studies are reported of total and partial-channel photoexcitation and ionization cross sections in carbon dioxide. As in previously reported studies of discrete and continuum dipole spectra in diatomic (N2, CO, O2, F2) and polyatomic (H2O, H2CO, O3) molecules in this series, separated-channel static-exchange calculations of vertical-electronic transition energies and oscillator strengths and Stieltjes-Tchebycheff moment methods are employed in the development. Detailed comparisons are made of the static-exchange excitation and ionization spectra with photoabsorption, electron-impact excitation, and quantum-defect estimates of discrete transition energies and intensities, and with partial-channel photoionization cross sections obtained from fluorescence measurements and from tunable-source and (e,2e) photoelectron spectroscopy. The spectral characteristics of the various discrete series and continua are interpreted in terms of contributions from compact 2πu(π*), 5σg(σ*), and 4σu(σ*) virtual valence orbitals, and from more diffuse discrete and continuum Rydberg orbitals. The 2πu(π*) orbital is found to contribute to discrete excitation series, whereas the 5σg (σ*) and 4σu (σ*) orbitals generally appear in the photoionization continua as resonance-like diabatic valence features. Good agreement obtains between the calculated discrete excitation series and the results of a recent analysis of the available spectroscopic data. The calculated outer-valence-shell (1πg-1)X 2Πg...

Experimental and Theoretical Studies of Electrothermal Waves

Gilpin, Robert R.; Zukoski, Edward E.
Fonte: AIAA Publicador: AIAA
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em //1969
Relevância na Pesquisa
45.7%
Experimental and theoretical studies have been made of the electrothennal waves occurring in a nonequilibrium electrical discharge in a potassium-seeded argon plasma. The studies presented in this paper refer to discharges in transverse gas flow and magnetic field. The behavior of these discharges as determined by photographs, photomultiplier measurements, and voltage probes is discussed and the results interpreted in terms of a steady, one-dimensional theory. A single discharge was found to operate in one of three modes-the shorted, transition, or normal mode-depending on the length of the ionization transient. An extension of the one-dimensional theory to the inlet problem predicts the approximate length of this transient and thus provides criteria for the existence of each mode. The normal mode was studied in a duct with a series of circuits discharging in parallel across a gas flow. Here, a regular set of steady, one-dimensional streamers was found in the center of the duct between hot boundary regions along each electrode wall. The properties of the one-dimensional streamers are shown to agree in detail with values predicted from the one-dimensional theory. A scheme is then presented for calculation of the effective conductivity of a duct using the amplitude of conductivity fluctuations predicted by this theory.

Photoexcitation and ionization in molecular oxygen: Theoretical studies of electronic transitions in the discrete and continuous spectral intervals

Gerwer, A.; Asaro, C.; McKoy, B. V.; Langhoff, P. W.
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 01/01/1980
Relevância na Pesquisa
45.78%
Theoretical studies of valence-electron (1πg, 1πu, 3σg) photoexcitation and ionization cross sections in molecular oxygen are reported employing separated-channel static-exchange calculations and the Stieltjes–Tchebycheff moment-theory technique. As in previously reported investigations of photoexcitation and ionization in small molecules following this approach, canonical Hartree–Fock orbitals, large Gaussian basis sets, and many-electron eigenstates of correct symmetry are used in defining appropriate noncentral static-exchange potentials and in computations of the appropriate discrete and continuum transition strengths. It is particularly important in molecular oxygen to incorporate the appropriate ionic parentages of the various photoionization multiplet states in order to obtain the correct partial-channel cross sections. The calculated discrete series associated with 1πg excitation are found to be in good agreement with available experimental assignments and previously reported theoretical studies, and the predicted states associated with 1πu and 3σg excitations are in general accord with assignments for the higher series based on spectral and quantum-defect analysis. Although the observed photoelectron spectra and photoionization cross sections are relatively complex...