Ion-Atom Collisions Electron capture reactions in N2 , O2 H

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Ion-Atom CollisionsElectron capture reactions in
N2, O2 H
patricia.barragan_at_uam.es barragan_at_phys.ksu.edu

• Patricia Barragán
• Laboratorio asociado al CIEMAT de Física Atómica
  y Molecular en Plasmas de Fusión
• Departamento de Química, Universidad Autónoma de
  Madrid

September 28, 2005
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Motivation

• Fusion plasmas.
• Plasma-wall interaction
  Impurities.
• Plasma diagnostics (CXS).

• Astrophysics.
• Comets X-ray emission .

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• N2 H and O2 H collisions.
• Presence of metastable ions in beams.
• Calculation of rate coefficients.
• Computational characteristics
• Many electron systems. Use of Quantum Chemistry
  techniques.
• Calculation in a wide energy range Quantal and
  semiclassical treatments.

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N2 H collisions
Reaction (1)
Reaction (2)
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O2 H collisions

• Reaction (3)

Reaction (4)
Reaction (5)
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Quantal treatment

• Schrödinger equation
• Boundary conditions (one electron systems)

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Molecular expansion
?k are eigenfunctions of Helec
? is the Common Reaction Coordinate, which
ensures that a truncated expansion satisfies the
scattering boundary conditions
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Cross Sections
are solutions of the system of differential
equations
The total Cross Section for transition i?j is
given by
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Semiclassical treatment

• The nuclei follow straight-line trajectories
• The electronic motion is described by the eikonal
  equation
• Molecular close-coupling treatment
• where D(r,t) is a common translation factor.

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Cross Sections

where the probability Pij for transition to the
final state is calculated from the coefficient
aj(t)
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Computational scheme

• Calculation of electronic energiesMRCI (MELDF)
• - GTO bases (Widmark et al. Theor.Chim. Acta. 77,
  291 (1990))
• - 80 reference configurations, iterative process
  to select the set of reference configurations at
  each R.
• - Frozen core approximation.
• - Perturbative selection.
• Calculation of dynamical couplings.
• - Numerical differentation (Castillo et al. J
  Chem. Phys. 03,2113(1995))
• - Sign consistency calculation of the delayed
  overlap matrix (Errea et al. J Chem. Phys.
  121,1663 (2004))

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N2 H Potential energy curves singlets
c.e.
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N2 H Potential energy curves triplets
c.e.
c.e.
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N2 H Potential energy curves triplets
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N2 H Potential energy curves triplets
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N2 H Potential energy curves quintets
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N2 H Total cross sections
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N2 H Total cross sections
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N2 H Total cross sections
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N2 H Total cross sections
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N2 H Branching ratios
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O2 H Potential energy curves doublets
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O2 H Potential energy curves cuadruplets
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O2 H Total cross sections
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O2 H Total cross sections
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O2 H Branching ratios
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Rate coefficients
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Rate coefficients
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Concluding remarks

• N2 H, O2 H collisions.
• Quantal calculation for low energy and
  semiclassical for high energy.
• Presence of metastable ions in beams Possible
  presence of N2(2s2p2 4P) in merged beams
  experiments. Not noted in other experiments.
• Very large cross sections at low energies - shape
  resonances?
• Calculation of partial EC cross sections
  (diagnostics).

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Thanks to

• L. Méndez, I. Rabadán, L. F. Errea and A. Riera
• who have participated directly in this work.
• And the other group members
• L. Fernández, F. Guzmán, C. Illescas, A. Macías
• and J. Suarez
• Group web-site http//tcam.qui.uam.es