Scaling behaviour of positronium formation cross sections for positron scattering from hydrogen-like ions

Abstract

Positronium (Ps) formation processes of hydrogen (H)-like ions by positron impact are investigated by employing the two-centre two-channel eikonal final state-continuum initial distorted wave model. The differential and integrated cross sections for Ps formation into the ground state are calculated for ions A (Z−1)+ with nuclear charge Z = 1-9. Comparisons with the first-order Coulomb-Born and the continuum distorted-wave final-state models are made. The differential cross sections and the Thomas double-scattering processes for H-like ions are investigated. For the integrated Ps formation cross sections, a scaling law is introduced and it is reasonably followed by H-like ions with Z 3 in the entire energy range. The maximum positions of the ground Ps formation cross sections for the H-like isoelectronic sequences are found to be in good agreement with the wave vector matching model of Charlton (2006

Rydberg transitions for positron–hydrogen collisions: asymptotic cross section and scaling law

“…For large values of l, the cross section is very small the relative error in estimating the cross section with the scaling law gets increased. It is to be mentioned here that the cross section for electron impact excitation and rearrangement processes also follows a 1/n 3 type scaling law [32,[36][37][38][39]. But in that case the scaling factor is rather different.…”

Positronium formation for positron scattering from metastable hydrogen

“…A detailed description of the EFS-CDW model to study the Ps formation in arbitrary states by positron scattering from atoms or ions can be found in our previous work. [18][19][20] Here, we briefly review the essential features of the method. Unlike the process in other distorted-wave formalisms where a distortion potential is constructed initially and from which the distorted wave can be obtained, we firstly define the initial and final states of the scattering system by continuum distorted and eikonal wave functions, respectively, to approximately represent the distortion effects of the Coulomb potentials in both the entry and exit channels,…”

“…The relationship between the present EFS-CDW method and the Born expansions has been discussed above. Details of the scattering mechanism of Thomas double-scattering in either quantum or classical pictures are available everywhere [19,29,30] and will not be discussed here. Another quite interesting phenomenon is the increasing of oscillation characters of the Thomas peak when Ps is formed in higher s-states.…”

“…In our previous work, [18][19][20] we have developed the twocenter, two-channel eikonal final state continuum initial distorted wave (EFS-CDW) method proposed originally by Macri et al [21,22] to study the Ps formation in arbitrary final states for neutral hydrogen atom and hydrogen-like ions by positron impact from low to high energies. All our previous work were done for targets in their ground states and the calculated results compare nicely with experimental measurements and other state-of-art theoretical methods available in the literature.…”

Positronium formation for positron scattering from helium ion

“…In our previous work [22,23], we developed a modified eikonal final state-continuum initial distorted wave (EFS-CDW) method initiated by Macri et al [24] and successfully extended it to the arbitrary excited-state Ps formation process. By using such a model we have investigated the Ps(1s) formation processes of hydrogen-like ions, including He + .…”