Quantum dynamics of the charge transfer in C⁺+ S at low collision energies

Abstract

Following a recent semiclassical investigation by Bacchus-Montabonel M C and Talbi D (2008 Chem. Phys. Lett. 467, 28), the C + (2s 2 2p) 2 P + S(3s 2 3p 4 ) 3 P charge transfer process involved in the modellisation of the interstellar medium chemistry and its reverse reaction are revisited by combining a wave packet approach and semiclassical dynamics in a quasimolecular approach for doublet and quartet states. New radial non adiabatic coupling matrix elements have been calculated and the mixed treatment gives access to new precise values of the rate coefficients for the direct and reverse charge transfer processes. For this system, quantum and semiclassical results are in good agreement even at low collision kinetic energies. The dominance of the quartet states in the process is confirmed. In the quantum treatment, the collision matrix elements are extracted from wave packets by the flux method with an absorbing potential. The formation of resonances due to a centrifugal barrier is illustrated.Confidential: not for distribution.

Characterization of the MgO2+dication in the gas phase: electronic states, spectroscopy and atmospheric implications

“…Both of them were widely described elsewhere (see for instance ref. 39 for more details). For numerical semi-classical treatments, we used the EIKONXS program based on an efficient propagation method 40 for the direct reaction Mg…”

“…The collision matrix elements are extracted from wave packets by the flux method with a complex absorbing potential. 39,41 A priori, semi-classical approaches are only valid for incident energies greater than a few eV amu…”

“…42 Nevertheless, the comparison of time-dependent quantal wave packet and semi-classical approaches for charge transfer processes showed that the latter approach may be extended to lower collision energies with acceptable accuracies. 39 The rate constants k(T) were then calculated for a series of temperatures by averaging the corresponding cross sections s(E) over a Maxwellian velocity distribution at temperature T: Table 2). The nature of the wavefunction of this electronic state changes drastically at the avoided crossing with the upper 2 3 S À state (Fig.…”

Non-adiabatic interactions in charge transfer collisions

“…The divergence with quantum time-dependent approaches appears only at lower energies, below 10 V [24,25].…”

“…The collision dynamics have been calculated with the EIK ONX S program. The calculations have been extended over a wide collision energy range, from V to V , taking account of our previous study comparing semiclassical methods and wave-packet time-dependent quantum treatments [24,25].…”