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Theoretical vibrational-excitation cross sections and rate coefficients for electron-impact resonant collisions involving rovibrationally excited N2 and NO molecules
No full textElectron-impact vibrational-excitation cross sections, involving rovibrationally excited N2 and NO molecules, are calculated for collisions occurring through the nitrogen resonant electronic state N2(-) (X (2)Pi(g)), and the three resonant states of nitric oxide NO(-)( (3)Sigma(-), (1)Delta, (1)Sigma(+)). Complete sets of cross sections have been obtained for all possible transitions involving 68 vibrational levels of N2 (X (1)Sigma(+)(g)) and 55 levels of NO(X (2)Pi), for incident electron energy between 0.1 and 10 eV. In order to study the rotational motion in the resonant processes, cross sections have also been computed for rotationally elastic transitions characterized by the rotational quantum number J running from 0 to 150. The calculations are performed within the framework of the local complex potential model, using potential energies and widths optimized to reproduce the experimental cross sections available in the literature. Rate coefficients are calculated for transitions between all vibrational levels by assuming a Maxwellian electron energy distribution function in the temperature range from 0.1 to 100 eV. All numerical data are available at http://users.ba.cnr.it/imip/cscpal38/phys4entry/database.htm
Cross sections for 14-eV e-H(2) resonant collisions: Isotope effect in dissociative electron attachment
No full textThe process of dissociative attachment of electrons to molecular hydrogen and its isotopes in the energy range at approximately 14 eV is investigated. The dissociative electron attachment cross sections for all six hydrogen isotopes are calculated over an extended range of electron energies using the local complex potential model with the excited Rydberg (2)Sigma(+)(g) electronic state of H(2)(-) acting as the intermediate resonant state. A significant isotope effect in theoretical electron attachment cross sections is observed, in agreement with previous predictions and experimental observations. A two-parameter analytic expression for the cross section is derived from the theory that fits accurately the numerically calculated cross sections for all isotopes. Similarly, an analytic mass-scaling relation is derived from the theory that accurately reproduces the numerically calculated rate coefficients for all isotopes in the 0.1-1000 eV temperature range by using the rate coefficient for the H(2) isotope only. The latter is represented by an analytic fit expression with two parameters only
Cross sections for 14-eV e-H2 resonant collisions: Dissociative electron attachment
No full textThe dissociative electron attachment (DEA) process in electron-H(2) molecule collisions, involving the (2)Sigma(+)(g) excited electronic Rydberg state of molecular hydrogen ion H(2)(-), is investigated theoretically. The DEA cross section has been calculated within the local complex potential approximation. The convoluted cross section, which presents a peak located at the incident energy of about 14 eV, compares favorably with available experimental data
Molecular Physics of Elementary Processes Relevant to Hypersonics: Electron-Molecule Collisions
No full textNon-resonant, electron-impact, vibro-electronic excitation cross sections, involving vibrationally excited N2 molecules, to the mixed valence-Rydberg b,c,o 1Πu and b′,c′,e′ 1Σu+ singlet states are presented. These cross sections are calculated using the so-called similarity approach, accounting for the vibronic coupling among excited states, and
compared with the experiments and different theoretical calculations.
New cross sections for the electron-impact resonant vibrational excitation of CO2 molecule are calculated, for the symmetric stretching mode, as a function of the incident electron energy and for the transitions (υi , 0,0)→(υf , 0,0) with
υi = 0,1,2 and for some selected value of υf in the interval υi ≤ υf ≤10. A resonance potential curve and associated widths are calculated using the R-matrix method. Rate coefficients, calculated by assuming a Maxwellian electron energy
distribution function, are also presented for the same (υi,0,0)→(υf,0,0) transitions.
Electron-impact cross sections and rate coefficients for resonant vibrational excitations involving the diatomic species N2, NO, CO, O2 and H2, for multi-quantic and mono-quantic transitions, are reviewed along with the cross sections and rates for the process of the dissociative electron attachment to H2 molecule, involving a Rydberg excited resonant state of the H2- ion
Dissociative electron attachment to vibrationally excited H-2 molecules involving the (2)Sigma(+)(g) resonant Rydberg electronic state
No full textDissociative electron attachment cross sections (DEA) on vibrationally excited H-2 molecule taking place via the (2)Sigma(+)(g) Rydberg-excited resonant state are studied using the local complex potential (LCP) model for resonant collisions. The cross sections are calculated for all initial vibrational levels (v(i) = 0-14) of the neutral molecule. In contrast to the previously noted dramatic increase in the DEA cross sections with increasing v(i), when the process proceeds via the X (2)Sigma(+)(u) shape resonance of H-2, for the (2)Sigma(+)(g) Rydberg resonance the cross sections increase only gradually up to v(i) = 3 and then decrease. Moreover, the cross sections for v(i) >= 6 exhibit pronounced oscillatory structures. A discussion of the origin of the observed behavior of calculated cross sections is given. The DEA rate coefficients for all v(i) levels are also calculated in the 0.5-1000 eV temperature range. (C) 2011 Elsevier B.V. All rights reserved
Cross sections for 11-14-eV e-H2 resonant collisions: Vibrational excitation
No full textResonant vibrational excitation (RVE) cross sections have been calculated for the electron-H(2) molecule collisions in the energy range 11-14 eV involving the (2)Sigma(+)(g) excited electronic state of the molecular hydrogen ion H(2)(-). This state, whose threshold is located around 14 eV, gives rise to the so-called series a of the observed peaks in electron-impact differential cross-section measurements. The calculations have been performed within the local complex potential approximation by using the available theoretical potential energy and width for the (2)Sigma(+)(g) resonant state. The cross sections for all nu(i)=0 ->nu(f)=1-14 RVE transitions have been calculated. A satisfactory agreement of calculated cross sections with the available experimental data is obtained
Electron-impact vibrational excitation of vibrationally excited H-2 molecules involving the resonant (2)Sigma(+)(g) Rydberg-excited electronic state
No full textElectron-impact theoretical cross sections and rate coefficients for vibrational excitation of vibrationally excited H-2 molecules, occurring through the h(2)(-) resonant species in the (2)Sigma(+)(g) Rydberg-excited electronic state, are presented. The cross sections are calculated as functions of the incident electron energy by adopting the local-complex-potential model for resonant collisions and by using ab initio calculated molecular potentials and resonance widths. The calculations have been extended to all possible vibrational transitions linking all 15 vibrational levels of the electronic ground state of the H-2 molecule. The corresponding rate coefficients are also obtained as a function of the electron temperature by assuming a Maxwellian electron energy distribution function, and a simple analytical expression is derived. Finally, the present rate coefficients for the transitions starting from the lowest vibrational level of the H-2 molecule are compared with those for the process involving the X-2 Sigma(+)(u) resonant state of the h(2)(-) molecular ion
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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