Two-center convergent close-coupling approach to positron–helium-ion collisions

Calculations of ionization and electron-capture cross sections in ion-atom collisions usually require solving the Schrödinger equation governing the collision system by expanding the total scattering wave function in a basis of target- and projectile-centered pseudostates. This approach leads to the two-center close-coupling equations which in some cases may become ill-conditioned due to the non-orthogonality of the underlying combined basis. Here we develop a technique which allows to accurately extract the necessary collision information, including that for the rearrangement channels, from the computationally more convenient one-center close-coupling equations which are built from only target-centered pseudostates. The robustness of the method is demonstrated by considering the proton-hydrogen scattering problem across a wide incident energy range. The developed method is then applied to study proton scattering on multielectron target of lithium. The obtained results for the 2s → 2p excitation and the total electron-capture cross sections are in good agreement with corresponding experimental data. It is concluded that the presented technique could be a simpler alternative when integrated cross sections are required.

Section: Discussionmentioning

confidence: 99%

One-center close-coupling approach to two-center rearrangement collisions

Abdurakhmanov

Plowman

Kadyrov

et al. 2020

“…Within the CCC method the two-centre approach has been applied to positron scattering from atoms [26] and H 2 [27,28]. However, the two-centre approach is computationally demanding and relatively complicated to implement, particularly for charged targets [29,30]. An attractive alternative is a single-centre formulation, which utilises an expansion on the target centre only.…”

Section: Methodsmentioning

confidence: 99%

Calculations of positron scattering on the hydrogen molecular ion

Mori

Utamuratov

Scarlett

et al. 2019

Positron scattering from the vibrational ground state of the hydrogen molecular ion has been investigated using the single-centre convergent close-coupling (CCC) method. Cross sections for dissociative excitation, dissociative ionisation, total inelastic scattering, and proton production have been calculated at incident positron energies from 10 to 500 eV. For this energy range the mass stopping power and mean excitation energy have also been calculated for both the positron and electron cases. Since there are no experiments or other calculations for positron scattering on the hydrogen molecular ion, the obtained results have been compared with corresponding CCC results for positron collisions with He+ and electron collisions with . Comparative analysis allows to estimate the quality of the approximations used in the present calculations.

“…4.2. scattering in e + e À He + + system Positron-positive helium ion is an example of positron-atomic target scattering in which asymptotic Coulomb interaction is present in one of the configurations. There are a number of calculations in a wide energy region, among them are close coupling calculations using two center basis functions expansion [40,41] and EFS-CDW method [42]. But to the best of our knowledge, there is lack of published results of calculation for the low-energy region.…”

Section: 1mentioning

confidence: 99%

High resolution calculations of low energy scattering in e⁻e⁺p¯ and e⁺e⁻He⁺⁺ systems via Faddeev–Merkuriev equations

Gradusov

Roudnev

Yarevsky

et al. 2019

The potential splitting approach incorporated into the framework of Faddeev-Merkuriev equations in the differential form is used for calculations of multichannel scattering in e − e +p and e + e − He ++ systems. Detailed calculations of all possible Swave cross-sections are performed in the low-energy region which supports up to seven open channels including the rearrangement channels of ground and excited states of antihydrogen, positronium and helium ion formations. All known sharp resonances of the systems obtained and approved by a number of authors are clearly reproduced in the calculated cross sections. In cross sections for energies above the threshold corresponding to n = 2 state of antihydrogen the prominent oscillations of Gailitis Damburg type have been found.