Chapter 6
Charge Transfer Rate Constants in Ion-Atom
and Ion-Molecule Processes
M.C. Bacchus-Montabonel
Abstract The theoretical treatment of charge transfer processes in collisions of ions
with atomic and molecular targets is developed using ab initio molecular calculations. An analysis of quantum and semi-classical dynamics is presented in order to
determine the limit of validity of such methods. Accurate cross sections and rate
constants are determined which provide important data for space chemistry models. Additionally, such theoretical approaches give an insight into the mechanism of
these processes with consideration of anisotropic effects for collisions with diatomic
molecular targets.
6.1 Introduction
Charge transfer processes are involved in the description of a number of astrophysical environments, astrophysical plasmas, interstellar medium, atmospheres of planets and stars. . . The knowledge of their rate constants is determinant for the modelisation of these mediums. However experimental data remain very scarce and theoretical approaches appear to be a very efficient tool for evaluation of such rate
constants. With regard to the environment, the temperature and consequently the
energy to be considered in the collision process may vary significantly, from 10 K
for example in the interstellar medium, to more than 10 4 K in some stellar environments. This requires developing different collision approaches in order to analyze
such processes. Charge transfer recombination with neutral atoms has been widely
investigated; this is indeed a fundamental process in the description of the interstellar medium which drives the ionization balance of charged species [1–5]. But
charge transfer between multiply charged ions and molecular targets has also to be
taken into account and appears to play a quite important role [6, 7]. In that sense, we
present in this paper significant results on collisions of carbon ions with atomic and
molecular targets. First of all, we consider the C + ( 2 P) + S( 3 P) collision and its reverse reaction which is determinant in the chemistry of sulfur and carbon species. It
M.C. Bacchus-Montabonel (B)
Institut Lumière Matière, UMR5306, Université Lyon 1-CNRS, Université de Lyon,
69622 Villeurbanne Cedex, France
e-mail: bacchus@univ-lyon1.fr
M. Hotokka et al. (eds.), Advances in Quantum Methods and Applications in
Chemistry, Physics, and Biology, Progress in Theoretical Chemistry and Physics 27,
DOI 10.1007/978-3-319-01529-3_6,
© Springer International Publishing Switzerland 2013
119
Charge Transfer Rate Constants in Ion-Atom
and Ion-Molecule Processes
M.C. Bacchus-Montabonel
Abstract The theoretical treatment of charge transfer processes in collisions of ions
with atomic and molecular targets is developed using ab initio molecular calculations. An analysis of quantum and semi-classical dynamics is presented in order to
determine the limit of validity of such methods. Accurate cross sections and rate
constants are determined which provide important data for space chemistry models. Additionally, such theoretical approaches give an insight into the mechanism of
these processes with consideration of anisotropic effects for collisions with diatomic
molecular targets.
6.1 Introduction
Charge transfer processes are involved in the description of a number of astrophysical environments, astrophysical plasmas, interstellar medium, atmospheres of planets and stars. . . The knowledge of their rate constants is determinant for the modelisation of these mediums. However experimental data remain very scarce and theoretical approaches appear to be a very efficient tool for evaluation of such rate
constants. With regard to the environment, the temperature and consequently the
energy to be considered in the collision process may vary significantly, from 10 K
for example in the interstellar medium, to more than 10 4 K in some stellar environments. This requires developing different collision approaches in order to analyze
such processes. Charge transfer recombination with neutral atoms has been widely
investigated; this is indeed a fundamental process in the description of the interstellar medium which drives the ionization balance of charged species [1–5]. But
charge transfer between multiply charged ions and molecular targets has also to be
taken into account and appears to play a quite important role [6, 7]. In that sense, we
present in this paper significant results on collisions of carbon ions with atomic and
molecular targets. First of all, we consider the C + ( 2 P) + S( 3 P) collision and its reverse reaction which is determinant in the chemistry of sulfur and carbon species. It
M.C. Bacchus-Montabonel (B)
Institut Lumière Matière, UMR5306, Université Lyon 1-CNRS, Université de Lyon,
69622 Villeurbanne Cedex, France
e-mail: bacchus@univ-lyon1.fr
M. Hotokka et al. (eds.), Advances in Quantum Methods and Applications in
Chemistry, Physics, and Biology, Progress in Theoretical Chemistry and Physics 27,
DOI 10.1007/978-3-319-01529-3_6,
© Springer International Publishing Switzerland 2013
119