1,721,017 research outputs found
Plasma Science for Aerospace and Thermonuclear Fusion Applications
No full textTheoretical applications of plasma science to space and thermonuclear fusion technologies is illustrated. In particular, the role of molecular non equilibrium plasmas in problems arising in re-entry conditions of space vehicles impacting on the atmosphere of a planet, in space explorations, and low temperature processes occurring in nuclear fusion tokamaks, is discussed. Particular emphasis is placed on the link between elementary processes occurring in the plasma at the microscopic level and the macroscopic behavior. In particular, recent results on cross section calculations for resonant electron-molecule collisions, involving N2, O2 and H2 molecules, are presented along with an application to the temporal evolution of a nitrogen plasma toward the thermal equilibrium
Electron collisions with excited molecules in low temperature plasmas
Full text linkState-to-state vibrationally resolved cross sections for electron-impact processes
involving vibrationally excited molecules are reviewed, with particular emphasis on
atmospheric and fusion plasma applications
Computational Astrobiology in Bari University and ISTP-CNR
No full textIn this contribution, we will present some results from our latest studies in the field of computational astrobiology, which are devoted to improving our understanding of the origin and evolution of life in the Universe by means of theoretical and computational models. The phenomena that can be studied by means of numerical modeling range from the micro to the macro scale, from molecules to cosmic grains and communities of primordial organisms. These studies may help to develop a global view of the phenomena involved in the origin of life in the wider context of astrobiology
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
Dissociative electron attachment and electron-impact resonant dissociation of vibrationally excited O2 molecules
Full text linkState-by-state cross sections for dissociative electron attachment and electron-impact dissociation for molecular oxygen are computed using ab initio resonance curves calculated with the R-matrix method. When O2 is in its vibrational ground state, the main contribution for both processes comes from the 2Pi_u resonance state of O2− but with a significant contribution from the 4Sigma−_u resonant state. Vibrational excitation leads to an increased contribution from the low-lying 2Pi_g resonance, greatly increased cross sections for both processes, and the threshold moving to lower energies. These results provide important input for models of O2-containing plasmas in nonequilibrium conditions
Resonant vibrational-excitation cross sections and rate constants for low-energy electron scattering by molecular oxygen
No full textResonant vibrational-excitation cross sections and rate constants for electron scattering by molecular oxygen are presented. Transitions between all 42 vibrational levels of O2(X (3)Sigma(-)(g)) are considered. Molecular rotations are parametrized by the rotational quantum number J, which is considered in the range 1-151. The lowest four resonant states of O2(-), (2)Pi(g), (2)Pi(u), (4)Sigma(-)(u) and (2)Sigma(-)(u) are taken into account. The calculations are performed using the fixed-nuclei R-matrix approach to determine the resonance positions and widths, and the boomerang model to characterize the nuclei motion. Two energy regions below and above 4 eV are investigated: the first one is characterized by sharp structures in the cross section and the second by a broad resonance peaked at 10 eV. The computed cross sections are compared with theoretical and experimental results available in the literature for both energy regions, and are made available for use by modelers. The effect of including rotational motion is found to be non-negligible
Rate coefficients for dissociative attachment and resonant electron-impact dissociation involving vibrationally excited O2 molecules
No full textRate coefficients for dissociative electron attachment and electron-impact dissociation processes, involving vibrationally
excited molecular oxygen, are presented. Analytical fits of the calculated numerical data, useful in the applications,
are also provided
Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule
Full text linkVibrational-excitation cross sections of ground electronic states of a carbon dioxide molecule by electron-impact through CO shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume a decoupling between normal modes and employ the local complex potential model for the treatment of nuclear dynamics, usually adopted for electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and a comparison with data present in the literature is discussed
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
Electron-impact resonant vibration excitation cross sections and rate coefficients for carbon monoxide
No full textResonant vibrational and rotation–vibration excitation cross sections for electron–CO
scattering are calculated in the 0–10 eV energy range for all 81 vibrational states of CO,
assuming that the excitation occurs via the 2 shape resonance. Static exchange plus
polarization calculations performed using the R-matrix method are used to estimate resonance
positions and widths as functions of internuclear separation. The effects of nuclear motion are
considered using a local-complex-potential model. Good agreement is obtained with available
experimental data on excitation from the vibrational ground state. Excitation rates and cross
sections are provided as a function of the initial CO vibrational state for all ground state
vibrational levels
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