| 1. |
- Froelich, Piotr, et al.
(författare)
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Four-body treatment of the antihydrogen-positronium system : binding, structure, resonant states and collisions
- 2019
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Ingår i: Hyperfine Interactions. - : Springer. - 0304-3843 .- 1572-9540.
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Konferensbidrag (refereegranskat)abstract
- We have developed a coupled-rearrangement-channel method allowing the rigorous non-adiabatic treatment of the multi-channel scattering problem for four particles. We present the study of the binding, resonant and collisional properties of the (H) over bar -Ps system with the total angular momentum J = 0(+) (singlet positronic configuration). The binding energy, the life-times of the resonant states and the collisional cross sections are calculated and discussed. We present the preliminary cross sections for the elastic and inelastic (H) over bar -Ps scattering, notably for the excitation of Ps and for the rearrangement reaction producing the (H) over bar (+) ions.
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| 2. |
- Piszczatowski, Konrad, et al.
(författare)
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Four-body calculations of elastic scattering in H-H collisions
- 2014
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Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 228:1-3, s. 85-89
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Tidskriftsartikel (refereegranskat)abstract
- We present a nonadiabatic treatment of the hydrogen-antihydrogen system. The technique used to describe H- H collisions is based on the coupled rearrangement channels method. Within this approach the total, nonadiabatic wave function of the system is divided into two parts: an inner and an outer one. To describe the inner part a set of square-integrable 4-body functions is used. These functions are obtained by a diagonalization of the total Hamiltonian projected on a chosen L2 subspace, they explicitly contain components of various arrangement channels expressed in terms of corresponding Jacobi coordinates. The outer part of the total wave function reflects its asymptotic character. Our procedure leads to the system of non-local integro-differential equations that are solved iteratively and simultaneously determine both the shape of the outer part of the wave function and the coefficients in the four-body expansion of the inner part. Using this formalism we perform the one-channel calculation of the elastic scattering to obtain the S-matrix and nonadiabatic scattering length.
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| 3. |
- Piszczatowski, Konrad, et al.
(författare)
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Nonadiabatic treatment of hydrogen-antihydrogen collisions
- 2014
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 89:6, s. 062703-
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Tidskriftsartikel (refereegranskat)abstract
- We present a nonadiabatic treatment of the hydrogen-antihydrogen system. The technique used to describe H-(H) over bar collisions is based on the coupled-rearrangement-channel method. Within this approach the total, nonadiabatic wave function of the system is divided into two parts: an inner and an outer one. To describe the inner part a set of square-integrable four-body functions is used. These functions are obtained by a diagonalization of the total Hamiltonian projected on a chosen L-2 subspace; they explicitly contain components of various arrangement channels expressed in terms of corresponding Jacobi coordinates. The outer part of the total wave function reflects its asymptotic character. Our procedure leads to a system of nonlocal integrodifferential equations that are solved iteratively and simultaneously determine the outer part of the solution and the coefficients in the four-body expansion of the inner part. To solve these equations the compact fine difference method was applied. Using this formalism we perform a one-channel calculation of the elastic scattering to obtain the S matrix, the nonadiabatic scattering length, and the cross section for the low-energy elastic scattering in the H-(H) over bar channel.
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| 4. |
- Stegeby, Henrik, et al.
(författare)
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Resonance states in the hydrogen-antihydrogen system from a nonadiabatic treatment
- 2016
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 49:1
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Tidskriftsartikel (refereegranskat)abstract
- The quantum-mechanical four-body problem for the hydrogen-antihydrogen system has been solved by means of the variational implementation of the coupled-arrangement channel method. Wave functions have been formed using the Gaussian expansion method (GEM) in Jacobi coordinates; they explicitly include components corresponding to the rearrangement from hydrogen and antihydrogen (H + (H) over bar into protonium and positronium (Pn + Ps). We analyze the solutions belonging to the discretized spectrum of the four-body eigenvalue problem, searching for resonance states at energies just below the H-(H) over bar dissociation energy threshold by means of the stabilization method and complex scaling.
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| 5. |
- Stegeby, Henrik, 1979-, et al.
(författare)
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Two-Body Hadronic Densities From The Four-Body Wave Functions For The Hydrogen-Antihydrogen System
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The quantum-mechanical four-body problem for the hydrogen-antihydrogen system has beensolved by means of the variational implementation of the coupled-arrangement channel method.The wave functions have been formed using the Gaussian expansion method (GEM) in Jacobi co-ordinates; they explicitly include components corresponding to the rearrangement from hydrogen and antihydrogen (H + H') into Protonium and Positronium (Pn + Ps). We analyse the solutionsbelonging to the discretized spectrum of the 4-body eigenvalue problem at energies correspondingto the low energy H { Hcollisions. Two-body nuclear correlation functions are calculated from thefour-body wave functions, as to investigate the proton-antiproton motion in the region of rearrangement from H+H' to Pn+Ps. We monitor the adiabatic versus nonadiabatic behavior of the system asa function of internuclear separation and nd that outside the rearrangement region the adiabaticdescription is quite adequate. The nonadiabatic behavior signicantly in uences the nuclear motionin the rearrangement region and reduces the rate of proton-antiproton annihilation in low-energy hydrogen-antihydrogen collisions.
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| 6. |
- Stegeby, Henrik, et al.
(författare)
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Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential
- 2012
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Ingår i: CENTRAL EUROPEAN JOURNAL OF PHYSICS. - : Walter de Gruyter GmbH. - 1895-1082. ; 10:5, s. 1038-1053
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Tidskriftsartikel (refereegranskat)abstract
- The problem of proton-antiproton motion in the H- system is investigated by means of the variational method. We introduce a modified nuclear interaction through mass-scaling of the Born-Oppenheimer potential. This improved treatment of the interaction includes the nondivergent part of the otherwise divergent adiabatic correction and shows the correct threshold behaviour. Using this potential we calculate the vibrational energy levels with angular momentum 0 and 1 and the corresponding nuclear wave functions, as well as the S-wave scattering length. We obtain a full set of all bound states together with a large number of discretized continuum states that might be utilized in variational four-body calculations. The results of our calculations gives an indication of resonance states in the hydrogen-antihydrogen system.
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| 7. |
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| 8. |
- Yamashita, T., et al.
(författare)
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Towards prediction of the rates of antihydrogen positive ion production in antihydrogen-excited positronium reaction
- 2020
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Ingår i: 31St International Conference On Photonic, Electronic And Atomic Collisions (Icpeac Xxxi). - : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- We present the 4-body calculation of the antihydrogen-positronium scattering aiming at the prediction of cross sections for the production of antihydrogen positive ions. The latter are expected to be a useful source of ultra-cold atoms for the test of matter-antimatter gravity. We convert the Schrodinger equation to a set of coupled integro-di fferential equations that involve intermediate states and are solved using the compact finite di fference method. We will present the investigation of the rearrangement reaction between the ground-state antihydrogen atom and the excited positronium.
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| 9. |
- Yamashita, T., et al.
(författare)
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Towards prediction of the rates of antihydrogen positive ion production in collision of antihydrogen with excited positronium
- 2020
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Ingår i: 31St International Conference On Photonic, Electronic And Atomic Collisions (Icpeac Xxxi). - : IOP PUBLISHING LTD.
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Konferensbidrag (refereegranskat)abstract
- We present a 4-body calculation of scattering between an antihydrogen atom ((H) over bar) and a positronium (Ps) aiming at the prediction of cross sections for the production of antihydrogen positive ions (($H) over bar (+)). The antihydrogen positive ions are expected to be a useful source of ultra-cold anti-atoms for the test of matter-antimatter gravity. We convert the Schrodinger equation to a set of coupled integro-differential equations that involve intermediate states which facilitate the internal region description of the scattering wavefunction. They are solved using a compact finite difference method. Our framework is extended to scattering between an excited Ps and (H) over bar. Cross sections of the reactions, Ps (1s/2s/3s) + (H) over bar -> e(-) + (H) over bar (+), in s-wave collisions, are calculated. It is found that the reactions originating from Ps (1s/2s) + H produce (H) over bar (+) with a constant cross section within 0.05 eV above the threshold while the reaction cross section from Ps (3s) decreases as the collision energy increases in the same energy interval. Just above the threshold, the cross section of (H) over bar (+) production from Ps (3s) + (H) over bar in s-wave collision is 7.8 times larger than that from Ps (1 s) + (H) over bar in s-wave and 2.3 times larger than that from Ps (2s) + (H) over bar in s-wave. The near-threshold de-excitation reaction from Ps (3s) + (H) over bar occurs more rapidly than the (H) over bar (+) production.
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