Two-center dielectronic recombination in slow atomic collisions

Abstract

A free electron can form a bound state with an atomic center A upon photo emission (radiative recombination). In the presence of a neighboring atom B, such a bound state can, under certain conditions, be also formed via resonant transfer of energy to B, with its subsequent relaxation through radiative decay (two-center dielectronic recombination). This two-center process is very efficient in the 'static' case where A and B form a weakly bound system, dominating over singlecenter radiative recombination up to internuclear distances as large as several nanometers. Here we study its dynamic variant in which recombination occurs when a beam of species A collides with a gas of atoms B and show that, even though the average distance between A and B in collisions is orders of magnitude larger than the typical size of a bound system, the two-center recombination can still outperform the single-center radiative recombination.I.

Formation of H¯+ via radiative attachment of e+ to Jacob1, Zhang2, Müller3 et al. 2020Phys. Rev. ResearchSelf Cite60120View full textAdd to dashboardCite

“…In a recent paper [31] the process of two-center dielectronic recombination of an electron with an atomic center A was considered when electrons and a beam of slow atoms A move in a gas of atomic centers B. The results of [31] can be straightforwardly adapted to the process of two-center dileptonic attachment.…”

“…Considering, following [31], only distant collisions between antihydrogens and matter atoms B and making use of the results of [31], for the contribution from these collisions to the total formation rate for positive antihydrogen ions per unit of time (per one e + +H pair) via the two-center dileptonic mechanism we obtain…”

“…However, a simple formula for the averaged rate, which enables one to establish a direct correspondence with the case of 2CDA at a fixed distance betweenH and B, can be derived if we suppose the following: (i) the function f (p) can be factorized as f (p) = f (1) ε (ε p ) f (2) ( p ); (ii) the function f (1) ε (ε p ) is distributed over an energy range which covers the interval of the "quasiresonance" energies, ε a + ω B − v/b min ε p ε a + ω B + v/b min , and is much broader than this interval with f (1) ε (ε p ) noticeably varying on a scale much larger than δε p ∼ v/b min [i.e., within the energy interval essential for 2CDA f (1) ε (ε p ) is roughly a constant]. Then, taking into account that the continuum width E p 1 eV is much larger than δε p ∼ v/b min , we can obtain a rough estimate for the averaged rate given by (see [31])…”

“…where p r = 2ε p,r = √ 2(ε a + ω B ). Assuming for simplicity that all positrons are incident under the angle ϑ p = π/2 and are homogeneously distributed over the energy interval ε p , one can get (see [31])…”

“…As it follows from (12), (13), and (14) the results for 2CDA depend on the parameter b min . Based on the discussion of collisional two-center dielectronic recombination, given in [31], we set here b min = 5 a.u. (that enables one to satisfy all assumptions which our approach to the two-center process relies on).…”