Inelastic processes from vibrationally excited states in slow H^{+}+H_{2} and H+H_{2}^{+} collisions: Excitations and charge transfer (original) (raw)
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Chemical Physics, 1989
cross sections for the process e + H2( v) +e+ Ht +e+H+H*(n= 1-5) have been calculated by using the Gryzinski approximation in combination with the Franck-Condon density. A satisfactory agreement is found between the present v=O cross sections and corresponding theoretical and experimental results for the processes leading to unexcited H*( n= 1) and excited H* (n = 2-5 ) fragments. The role of vibrational excitation in affecting cross sections is such to decrease the threshold energy and to increase the maximum value of the cross section. This behaviour holds for all processes, with the exception of cross sections leading to H* (n = 2). In this last case the maximum value of the cross sections increases with increasing the vibrational quantum number v for vQ 5, having an opposite behaviour for v> 5.
Chemical Physics, 1995
Partially decoupled quantum mechanical calculations, termed VCC-RIOS in the main text, which occur in the H 2 molecule colliding with protons are carried out for the vibrational excitation processes. A broad range of collision energies, up to 70 eV, is examined and results are compared with existing data for average energy transfer, integral cross sections and differential cross sections. A very detailed comparison with various experiments is carried out at E = 20 eV and satisfactory agreement with both experiments and earlier calculations is found for several dynamical observables. Through the present, extensive study of the higher energy behaviour of cross sections it is possible to further test the quality of one of the existing PES and to confirm the mode of behaviour for the charge-transfer channels that open up as the molecule becomes vibrationally 'hot' during collisions. * Corresponding author. Fax: +39-6-49913305. E.mail:
Electron-Impact Dissociation of Vibrationally-Excited Molecular Hydrogen into Neutral Fragments
Atoms, 2019
We present convergent close-coupling (CCC) calculations of electron-impact dissociation of vibrationally-excited molecular hydrogen into neutral fragments. This work follows from our previous results for dissociation of molecular hydrogen in the ground vibrational level [Scarlett et al., Eur. Phys. J. D 72, 34 (2018)], which were obtained from calculations performed in a spherical coordinate system. The present calculations, performed utilizing a spheroidal formulation of the molecular CCC method, reproduce the previous dissociation cross sections for the ground vibrational level, while allowing the extension to scattering on excited levels.
Atomic Data and Nuclear Data Tables, 2001
An extensive cross section database for the electron-impact inelastic processes of vibrationally excited molecules of hydrogen and its isotopes is presented. The following inelastic processes are covered: electronic excitation (dissociative and nondissociative), direct ionization (dissociative and nondissociative), excitationradiative decay vibrational excitation and dissociation, and dissociative electron attachment. The data have been compiled partly from the literature and partly generated theoretically for the present report. The data are presented in graphical form. The data are also presented by sufficiently accurate analytic fit functions. Massscaling relations are provided for cross section evaluation of those isotope molecules for which calculated data are not available. C
Journal of Molecular Structure: THEOCHEM, 2001
We report a systematic study on the role played by electronic correlation of target on vibrational excitation processes of molecules by electron impact. More speci®cally, cross sections for vibrationally elastic and inelastic electron±H 2 collisions are reported in the 1.5±40 eV range. In our study, the electron±molecule interaction potential is derived using both the near-Hartree±Fock and the con®guration interaction target wavefunctions. The body-frame vibrational close-coupling equations are solved using the method of continued fractions (MCF). Our study has shown that the MCF is a very ef®cient method for solving such scattering equations. In addition, the calculated results have shown that the electronic correlation effects of target signi®cantly in¯uence the calculated vibrational excitation cross sections at low incident energies and for the excitations leading to high-lying vibrational levels. Nevertheless, these effects are not relevant at higher incident energies.
Vibrational Excitation ofH2by Proton Impact
Physical Review A
The forward-scattered component of the absolute cross sections for protonand deuteronimpact excitation of the first four vibrational levels of the electronic ground state of H2 have been measured. Excitation cross-section measurements are reported for laboratory energies from 100 to 1500 eV; and, for energies below 100 eV, excitation cross sections are reported for forward-scattered protons from 8=0' to 8=1.9'. The cross sections were measured from the peak intensities observed in the ion energy-loss spectra generated by passing a highquality proton beam (energy spread & 80 meV, angular divergence-+ 1') through a collision chamber containing the target gas at room temperature. Each excitation cross section (crp"i, where the quantum number v' refers to the final energy level) is found to reach a maximum value at an energy which decreases with increasing quantum number 'p': opl(max) = 1.37x 10 " cm at 200 eV, op2(max) =0. 342 x10 cm at140 eV, ando. p3(max) =0.078 && 10~" cm andg. p4(max) =0. 021x10 ' cm both at 110 eV. These maxima give collision times and distances which are consistent with the adiabatic hypothesis. For energies beyond the maxima, the cross sections decrease very slowly with increasing energy. Furthermore, the cross sections for excitation to the higher levels decrease more rapidly than the cross sections for excitation to the lower levels, an effect predicted by Shin in a three-dimensional calculation involving a semiclassical theory for the excitation of a classical harmonic oscillator. A comparison of our results with vibrational excitation studies of other systems demonstrates the unique features of the H'-H& system. The large values of these vibrational excitation cross sections and their wide effective kinetic energy span show that vibrational excitation must be an important process in a wide variety of physical phenomena.
Differential cross sections for near-threshold electron impact dissociation of molecular hydrogen
Journal of Physics B: Atomic, Molecular and Optical Physics, 2001
At low energies, the major pathway for the electron impact dissociation of H 2 is through excitation to b 3 + u . Ab initio calculations using the adiabatic nuclei, energy balance model of Stibbe and Tennyson (1998 New J. Phys. 1 2.1) of total cross sections, angular differential cross sections, energy differential cross sections and double differential cross sections for the electronic ground state initial vibrational v = 0 level, dissociating into continuum states are presented. The formal expressions needed for such calculations, which involve three fragments in the exit channel, are derived.
Impact Excitations of Hydrogen Atoms in Collisions with Protons and Antiprotons
The direct impact excitations of ground-state hydrogen atoms by protons and antiprotons are investigated by using an impact parameter treatment. The calculations are performed within the solution of the coupled differential equations arising from the one-center atomic-orbital close-coupling approach as well as the impact parameter version of the first and second Born approximations. We have considered calculations that allow couplings to the í µí±=1–5 states (up to g sub-levels) of the target atom as well as others, which neglect the effect of all states other than the initial and final states of the target atom. The sensitivity of the cross sections to the charge of the projectile is studied. The calculated cross sections are compared with those obtained by previous theoretical and experimental results.
Benchmark calculations of electron impact electronic excitation of the hydrogen molecule
Journal of Physics B: Atomic, Molecular and Optical Physics, 2020
We present benchmark integrated and differential cross-sections for electron collisions with H2 using two different theoretical approaches, namely, the R-matrix and molecular convergent close-coupling. This is similar to comparative studies conducted on electron–atom collisions for H, He and Mg. Electron impact excitation to the b 3 Σ u + , a 3 Σ g + , B 1 Σ u + , c3Πu, E F 1 Σ g + , C1Πu, e 3 Σ u + , h 3 Σ g + , B ′ 1 Σ u + and d3Πu excited electronic states are considered. Calculations are presented in both the fixed nuclei and adiabatic nuclei approximations, where the latter is shown only for the b 3 Σ u + state. Good agreement is found for all transitions presented. Where available, we compare with existing experimental and recommended data.
Resonant contributions to dissociation of H2by low-energy electron impact
Journal of Physics B: Atomic, Molecular and Optical Physics, 1993
A resonance theory of electron-impact vibrationd excitation of diatomic molecules is extended to the case where the final vibrational level of the molecule lies in the " h u m. 7he extended theory is applied to resonant dissoeiation of molecular hydrogen by low-energy electron impact. Theoretical moss sections for dissociation of ground-state H2 via the X '4 and B 2 C i resonance a~e presented and compared with thearetiad cmss sections obtained by other authors using non-resonant methods. An imponant aim of the present work is M study the effect of initial vibrational excitation on the dissociation cross section. It is found that fhe