title: Calcium-hydrogen interactions for collisional excitation and charge transfer.
abstract: The accurate highly correlated ab initio calculations for ten low lying covalent Σ+2 states of CaH molecule, and one ionic Ca+H-state, are performed using large active space and extended basis set, with special attention to the long-range (6-20 Å) region where a number of avoided crossings between ionic and covalent states occur. These states are further transformed to a diabatic representation using a numerical diabatization scheme based on the minimization of derivative coupling. This results in a smooth diabatic Hamiltonian which can be easily fit to an analytic form. The diagonal elements of the diabatic potentials were then empirically corrected to reproduce experimental dissociation energies. Though the emphasis is on the asymptotic region, the obtained spectroscopic constants are in good agreement with available experimental and theoretical data. The resulting analytical Hamiltonian, after back transformation to adiabatic representation, is used to obtain cross sections for different inelastic processes using both the multichannel and the branching probability current approaches. It is shown that while for most intense transitions both approaches provide very close results, the multichannel approach underestimates the cross sections of weak transitions, as a consequence of the short-range avoided crossings that are accounted for only in the branching probability current method.
authors.affiliation: Laboratoire Modélisation et Simulation Multi-Echelle, Université Paris-Est, UMR 8208 CNRS, 5 Bd Descartes, Marne la Vallée, Champs-sur-Marne F-77454, France.
authors.forename: A
authors.initials: A
authors.lastname: Mitrushchenkov
authors.affiliation: Laboratoire Modélisation et Simulation Multi-Echelle, Université Paris-Est, UMR 8208 CNRS, 5 Bd Descartes, Marne la Vallée, Champs-sur-Marne F-77454, France.
authors.forename: M
authors.initials: M
authors.lastname: Guitou
authors.affiliation: Department of Theoretical Physics and Astronomy, Herzen University, Moika 48, Saint Petersburg 191186, Russia.
authors.forename: A K
authors.initials: AK
authors.lastname: Belyaev
authors.affiliation: Department of Theoretical Physics and Astronomy, Herzen University, Moika 48, Saint Petersburg 191186, Russia.
authors.forename: S A
authors.initials: SA
authors.lastname: Yakovleva
authors.affiliation: LERMA, Observatoire de Paris, PSL Research University, Sorbonne University, UPMC University Paris 06, CNRS-UMR 8112, F-92195 Meudon, France.
authors.forename: A
authors.initials: A
authors.lastname: Spielfiedel
authors.affiliation: LERMA, Observatoire de Paris, PSL Research University, Sorbonne University, UPMC University Paris 06, CNRS-UMR 8112, F-92195 Meudon, France.
authors.forename: N
authors.initials: N
authors.lastname: Feautrier