Asymptotic theory of s→p charge exchange: Extended Demkov model

The asymptotic theory is developed for the calculation of the charge-exchange amplitudes for large impact parameters ρ. The case of the small energy defect is considered which corresponds to the Demkov model (nonadiabatic transitions induced by the switching of the wave functions from the atomic states to the molecular-orbital regime). The effect of electron momentum transfer is included. The initial and final states with nonzero orbital momentum are considered with a special emphasis on the simplest case of s→p charge exchange. The large-ρ asymptote of the charge-exchange amplitude is calculated both for the transitions induced by radial and rotational couplings. One-center depolarization transitions (changing the projection of the angular momentum) are also incorporated in the general theory. The orientation and alignment parameters characterizing the asymmetry created in the s→p process are obtained in a simple analytical form for large ρ (or small scattering angles). They include contributions both from the one-center depolarization and from the competition of the charge exchange induced by radial and rotational coupling. The relative role of both mechanisms is analyzed and a strong dependence of the asymmetry parameters on the sign of the process energy defect is predicted. The theory is applied to the process Na(3p)+H+→Na++H(n=2)