High-energy behaviour of the transition probabilities and total cross sections for charge exchange

Time-Dependent Density-Functional Theory for Determining the Electron-Capture Cross Section for Protons Impacting on Atoms and Molecules

The use of the Time-Dependent Density-Functional Theory (TDDFT) has increased in the atomic collision field. Calculating the electron-capture cross section (ECCS) for protons is an important question in hadrontherapy and plasma physics, among other areas. In previous studies, it was shown that the approach based on the Local Density Approximation (LDA) fails in the 1-50 keV region, requiring the use of the Optimized Effective Potential (OEP) method. In this work, the ECCS values for 1-50 keV protons impacting on isolated hydrogen, carbon, nitrogen, oxygen, and nitrogenous atoms were determined using the TDDFT. It is shown that adding the Self Interaction Correction to the LDA (LDA-Sic) allows obtaining results close to those provided by the OEP and experiments, with the advantage that the LDA-Sic consumes less computational time. In addition, it was demonstrated that it is imperative to include the spin correction for the specific helium and oxygen cases, in order to get good results for the ECCS using the TDDFT. Theoretical results obtained in this work show excellent agreement with experimental values.

Proton-hydrogen collisions: Differential and total cross sections for H(2s) and H(2p) production in the 1—7 keV range

A multistate molecular approach to the proton—hydrogen collision is formulated in terms of an impact parameter perturbed stationary-states approximation. Spurious long range couplings are avoided and Galilean invariance is enforced by the inclusion of momentum translation factors which are determined variationally within an Euler-Lagrange formalism (Crothers & Hughes 1978). Well defined radial and rotational coupling matrix elements are employed in the 1-7 keV impact energy range in a six-state (lso g , 2po u , 2pπ u , 3po u , 3pπ g , 4fo u ) calculation of elastic and inelastic differential scattering cross sections, charge exchange probabilities and both direct and exchange H (2p) production total cross sections. They are also employed in the same energy range in a ten-state (1so g , 2po u , 3dπ g , 2pπ u , 2so g , 3po u , 3do g , 4fo u , 4dπ g , 3pπ u ) calculation of both direct and exchange H (2s) production total cross sections. The results are in excellent accord with experimental data and show considerable improvement on previous molecular calculations. This success is attributed to the inclusion of both momentum translation factors and radial coupling matrix elements.