| 1. |
- Forrey, Robert C., et al.
(författare)
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Nonadiabatic coupling in cold collisions of spin-polarized metastable hydrogen atoms
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:5, s. 052709-
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Tidskriftsartikel (refereegranskat)abstract
- Previous calculations of low-temperature cross sections for collisions between spin-polarized metastable hydrogen atoms are improved to include nonadiabatic radial and angular coupling at large interatomic separations. The electrostatic dipole-quadrupole interaction produces nonadiabatic radial coupling between (2s,2p) and (2p,2p) states, while the Coriolis interaction produces nonadiabatic angular coupling. Both of these long-range contributions are handled in a space-fixed atomic gauge that is particularly convenient for a spin-polarized system. The improved theoretical results are compared with an existing experiment.
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| 2. |
- Jonsell, Svante, et al.
(författare)
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Stability of hydrogen-antihydrogen mixtures at low energies
- 2001
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 64:5, s. 052712-
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Tidskriftsartikel (refereegranskat)abstract
- The stability of antimatter in contact with matter has been investigated. The interaction between hydrogen and antihydrogen is considered as the prototype reaction. We have focused interest on the rates for proton-antiproton and/or electron-positron annih
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| 3. |
- Jonsell, Svante, et al.
(författare)
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Strong Nuclear Force in Cold Antihydrogen : Helium Collisions
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - New York, N.Y. : Publ. by the American Physical Society through the American Institute of Physics. - 1050-2947 .- 1094-1622. ; 70:6, s. 062708-
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Tidskriftsartikel (refereegranskat)abstract
- We calculate cross sections for elastic scattering and annihilation in antihydrogen-helium collisions at low energies. The calculations are based on the Born-Oppenheimer approximation, and incorporate the effects of the strong interaction through a scattering length approach. We find that the strong nuclear force not only causes significant annihilation, but also cannot be neglected in the elastic channel. In the zero energy limit we obtain the scattering length a=−7.69−3.80i a.u. for ground state antihydrogen-helium collisions. Annihilation is found to dominate over elastic scattering up to a temperature about 3 K. Loosely bound metastable antihydrogen-helium states are also investigated, and it is found that a number of relatively long-lived states with up to three units of angular momentum exist.
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| 4. |
- 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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| 5. |
- Vanne, Yulian, et al.
(författare)
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Doubly Excited Autoionizing States of H2 converging to the H(n=2) + H(n' = 2) Limit
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 73:6, s. 062706-
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Tidskriftsartikel (refereegranskat)abstract
- A numerical investigation of the doubly excited states of H2 converging to the H(n=2)+H(n′=2) limit was performed. Special emphasis was put on the accurate description of the range of intermediate internuclear distances in order to correctly connect the short range with the asymptotic van der Waals regime where perturbation theory is applicable. The present nonperturbative calculation extends to internuclear separations R=200a0 and is sufficiently accurate to achieve a connection between the two extreme regimes without any need for an interpolation procedure. The high precision of the ab initio results revealed a long range dipole-quadrupole interaction that had been omitted in two earlier calculations. In addition to revised first-order perturbation theory results the leading second-order term varying as R−6 was obtained. The impact of the present findings for cold H(n=2) collisions is briefly discussed.
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| 6. |
- Voronin, Alexei, et al.
(författare)
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Gravitational quantum states of Antihydrogen
- 2011
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 83, s. 032903-
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study of the motion of the antihydrogen atom ((H) over bar) in the gravitational field of Earth above a material surface. We predict that the (H) over bar atom, falling in the gravitational field of Earth above a material surface, would settle into long-lived quantum states. We point out a method of measuring the difference in the energy of (H) over bar in such states. The method allows for spectroscopy of gravitational levels based on atom-interferometric principles. We analyze the general feasibility of performing experiments of this kind. We point out that such experiments provide a method of measuring the gravitational force (Mg) acting on (H) over bar and that they might be of interest in the context of testing the weak equivalence principle for antimatter.
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| 7. |
- Voronin, Alexei, et al.
(författare)
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Hyperfine transitions in ultracold hydrogen : antihydrogen collisions
- 2009
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 80:1, s. 010502-
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Tidskriftsartikel (refereegranskat)abstract
- We consider the hyperfine transitions in ultracold collisions of hydrogen (H) and antihydrogen ((H) over bar) atoms. The cross sections for transitions between various spin states are calculated. We show that hyperfine transitions in (H) over bar -H collisions are basically driven by the strong force between proton and antiproton.
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| 8. |
- Voronin, Alexei, et al.
(författare)
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Interaction of ultracold antihydrogen with a conducting wall
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:6, s. 062903/1-062903/11
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the interaction of ultracold antihydrogen with a conducting surface, focusing on the phenomenon of quantum reflection. We calc. the reflection probability as a function of incident atom energy. We find that, for ground-state H atoms (with T<10-5 K), the probability of reflection is R.simeq.1-kb, where k is the momentum of the atom and b=2174.0 a.u. is a const. detd. solely by the van der Waals-Casimir tail of the atom-wall interaction. We show that quantum reflection, which suppresses the direct contact of ultracold atoms with the surface, allows for the possibility of confinement and storage of sufficiently cold antihydrogen atoms. We calc. the lifetime of H atoms enclosed in between solid walls. We develop a theory of H in a waveguide and propose some applications, notably the measurement of retardation corrections in the long-range component of the antiatom-wall potential. We demonstrate the existence of quantized states for antihydrogen atoms falling onto conducting surface in the gravitational field of Earth. We calc. the lifetime of ultracold H in its lowest gravitational state and obtain t=(Mgb/2h)-1.simeq.0.1 s, where Mg is a gravitational force acting on the antiatom. We propose that measurement of this lifetime may provide a new test for the gravitational properties of antimatter.
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| 9. |
- Voronin, A. Yu., et al.
(författare)
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Resonant phenomena in antihydrogen-hydrogen scattering
- 2008
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 77:2, s. 022505-
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Tidskriftsartikel (refereegranskat)abstract
- We present a treatment of cold hydrogen-antihydrogen collisions based on the asymptotic properties of atom-antiatom interactions. We derive general formulas for the elastic and inelastic cross sections and for the scattering lengths and analyze their sensitivity to the parameters characterizing the inelasticity of the collision process. Given the inelasticity, we obtain bounds for the complex scattering length. We investigate the influence of strong nuclear forces and the isotope effects in H (H) over bar and D (H) over bar collisions and demonstrate enhancement of these effects due to the presence of the near-threshold narrow H (H) over bar (D (H) over bar) states. The values of the elastic and inelastic cross sections with simultaneous account of rearrangement and strong forces are presented. General expressions for the (complex) energies of the near-threshold H (H) over bar states are obtained.
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| 10. |
- Wallenius, Jan, et al.
(författare)
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Formation of metastable dt mu molecules in t mu(2s)-D-2 collision
- 1996
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 54:2, s. 1171-1182
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Tidskriftsartikel (refereegranskat)abstract
- The formation process of metastable dt mu molecules in D-2-T-2 mixtures is investigated. The dt mu molecule exhibits a series of three-body resonances embedded in the t mu+d scattering continuum just below the t mu(2s)+d threshold, These states can-be for
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