Annihilation cross section of protonium by electron impact

Abstract

Cross sections for annihilation of protonium (Pn) induced by electron impact are calculated in a quantal close-coupling method, where the scattering wavefunction is expanded in terms of the atomic orbitals of protonium. The energy dependence of the annihilation cross sections and the decay mechanisms differ considerably for each initial n, ℓ state of Pn(nℓ), where n and ℓ are the principal and angular momentum quantum numbers. A similar study of the process but with heavy-particle impact by Sakimoto (2005 At. Mol. Opt. Phys. 38 3447) concluded that the annihilation cross section of Pn(nℓ) scales with n for each ℓ. This scaling rule, except for the initial p states at high energies, cannot be confirmed in the present study.

Cross sections for antiproton capture by helium ions

“…The total capture probabilities P J for the total angular momentum J = 32 at collision energies 0 E 1.82 eV obtained by using the accurate method and the approximation of Tong et al [21]. possibly by external fields) [38][39][40][41][42]. The L-mixing processes are very important for understanding the atomic cascade and the lifetime history ofpHe 2+ [3,30,31,38,39].…”

Annihilation cross sections of protonium by ion impact: scaling law with respect to the principal quantum number

“…As it is given above (see equation ( 1)), the energy shifts and widths of the ns states are much smaller than the energy differences between adjacent levels (| n − n±1 | ns , ns ), which indicate the predominance of the intra-shell transitions [11]. Therefore, in previous calculations, states belonging only to the manifold of the initial state (n 0 manifold) were considered to be coupled [9,10,12,13]. In the present CC calculation, transitions between different n (n = n 0 ) shells (inter-shell transition) are also taken into account.…”

“…Considerable progress has been made for a proper account of the process; however, the phenomenon is far from being well understood. Annihilation of Pn induced by charged particle impact has been reported recently [9,10,12,13]. Full quantum mechanical and semi-classical calculations were performed by Jensen and Markushin for the collision process with atomic hydrogen [9], where the energy shifts and widths of s states were introduced for the first time.…”