The 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.

Allowed vibronic transitions to the two lowest singlet electronic terms induced by electron impact in the cesium dimer are theoretically investigated in the frame of the semiclassical impact parameter method. All relevant quantities characterizing the transitions, i.e., transition dipole moments, Franck-Condon factors, and vibronic moments, are derived and compared with results in the literature. Total and vibrationally resolved cross sections for excitations initiated from. v '' = 0-45 vibrational levels of the ground electronic state are calculated and the role of vibrational excitation is discussed.

Resonant vibrational excitation cross sections and the corresponding rate coefficients for electron–N2 collisions occurring through the N2(X2Pg) resonant state are reviewed. New calculations are performed using accurate potential energy curves for the N2 electronic ground state, taken from the literature, and for the N2 resonant state, obtained from R-matrix calculations. The calculations are extended to resonant excitation processes involving the N2 ground state vibrational continuum, leading to dissociation. Electron-impact dissociation is found to be significant from higher vibrational levels. Accurate analytical fits for the complete set of the rate coefficients are provided. The behavior of the dissociative cross sections is investigated for rotationally excited N2 molecules, with J = 50, 100 and 150, and for different vibrational levels.

Resonant 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.

Electron-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.

Electron-impact cross sections are calculated for the v → v transitions occurring between the vibrational levels of the two X 2+ and A2 electronic states of the BeH molecule. The calculations are performed with the R-matrix method for a purely vertical electronic transition for energies from threshold to 15 eV, and by using a modified version of the Mott and Masssey approximation to extend the calculations to high energies and to vibrational excitations. Rate coefficients are also calculated for the same transitions. The calculated v–v selective cross sections and rate coefficients both satisfy distinct scaling relationships, which can be represented in a simple analytic form.

The role of internal degrees of freedom of molecular species in non-equilibrium plasmas is briefly outlined. Importance of collision cross sections for electron-impact with excited molecules in kinetic models is discussed, and few examples of some particular process in real plasma systems is illustrated. Some preliminary results of vibrational excitations by electron impact are shown.

State-to-state non-equilibrium plasma kinetics is widely used to characterize cold molecular and reentry plasmas. The approach requires a high level of dynamical information, and demands a large effort in the creation of complete databases of state-resolved cross sections and rate coefficients. Recent results, emphasizing the dependence of elementary process probability on both the vibrational and rotational energy content of the H2 molecule, are presented for those channels governing the microscopic collisional dynamics in non-equilibrium plasmas, i.e. electron-impact induced resonant processes, vibrational deactivation and dissociation in atom–diatom collisions and atomic recombination at the surface. Results for H2 plasmas, i.e. negative ion sources for neutral beam injection in fusion reactors, RF parallel-plate reactors for microelectronics, atmospheric discharges and the shock wave formed in the hypersonic entry of vehicles in planetary atmosphere for aerothermodynamics, are discussed.

Dissociative 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.

Theoretical 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.

Rate 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.

Non-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.

BeH+ molecules will be an important intermediary species present in fusion plasmas with Be walls (e.g. JET, ITER), both for impurity transport and spectroscopic studies. To enable such analyses the electron-impact-induced excitations X (1)Sigma(+)(v(i)) -> A (1)Sigma(+)(v(f)) and X (1)Sigma(+)(v(i)) -> B (1)Pi (v(f)) in BeH+(v(i)) molecular ion, occurring between the v(i) and v(f) vibrational levels of different electronic states (vibro-electronic transitions), have been studied using the Coulomb-Born approximation. The cross sections and rate coefficients for these transitions have been calculated in a broad energy and temperature range, respectively. Accurate analytic fit expressions have been derived for the cross sections and rate coefficients for the v(i) = v(f) = 0 case of considered electronic transitions that have correct asymptotic limits. It has been demonstrated that the cross sections and rate coefficients for v(i), v(f) > 0 transitions satisfy approximate (to within 10%) scaling relationships that involve the transition energies and matrix elements of dipole transition moments only.

Thermal non-equilibrium plasmas have been deeply investigated theoretically by means of the state-to-state approach, offering the unique opportunity of a detailed information about internal distributions affecting thermodynamics, transport coefficients and kinetics, properly accounting for the presence of excited states. The efforts made in the construction of knowledge on the dynamics of elementary processes occurring in the plasma with resolution on internal degrees of freedom, required by the method, are discussed. Boltzmann equation is solved for electrons self-consistently coupled to the chemical species collisional dynamics, reproducing very interesting features of strongly non-equilibrium internal distributions, characterizing plasmas.

Resonant 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.

Electron-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.html.

Diamond is considered as a very promising material for the development of devices for radiation detection. Unlike other conventional photoconductive detectors diamond-based devices should provide high discrimination between UV and visible radiation. In this work we present the electro-optical properties of devices based on randomly oriented diamond films, synthesized in a microwave plasma enhanced chemical vapor deposition reactor. A comparative study on devices with coplanar interdigitated Cr/Au electrodes (with different interelectrode pitches) made of films grown simultaneously on intrinsic and p-doped silicon (100) substrates has been performed. The chemical-structural, morphological, electrical and optical properties of ROD films have been studied. In particular, the optical response has been measured in air using a Xe flash lamp coupled with an optical quartz fiber and a properly tailored front-end electronics based on a charge sensitive amplifier. Experimental results gave indications on how the device performances are dependent on the two types of employed substrates. (C) 2011 Elsevier B.V. All rights reserved.