| 1. |
- Kjellsson Lindblom, Tor, et al.
(författare)
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Relativistic effects in photoionizing a circular Rydberg state in the optical regime
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 102:6
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Tidskriftsartikel (refereegranskat)abstract
- We study the photoionization process of a hydrogen atom initially prepared in a circular Rydberg state. The atom is exposed to a two-cycle laser pulse with a central wavelength of 800 nm. Before the atom approaches saturation, at field intensities of the order of 10(17) W/cm(2), relativistic corrections to the ionization probability are clearly seen. The ionization is predominantly driven by the radiation pressure in the propagation direction of the laser field, not by the electric field. Direct comparisons with the full numerical solution of the time-dependent Dirac equation demonstrate quantitative agreement with a semirelativistic approximation, which is considerably easier to implement.
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| 2. |
- Selstø, Sølve, et al.
(författare)
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Alternative descriptions of the light-matter interaction beyond the dipole approximation
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 76:2, s. 23427-
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Tidskriftsartikel (refereegranskat)abstract
- Different descriptions of the light-matter interaction which include the full spatial dependence of the electromagnetic field are presented. It is demonstrated how nondipole forms of both the Kramers-Henneberger and the length gauge Hamiltonians may be obtained from the minimum-coupling Hamiltonian in the velocity gauge through the Baker-Hausdorff lemma. Furthermore, the length gauge version of the Dirac equation is presented. The applicability of the different descriptions is discussed.
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| 3. |
- Skjerlie Simonsen, Aleksander, et al.
(författare)
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Ionization dynamics beyond the dipole approximation induced by the pulse envelope
- 2016
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Ingår i: Physical Review D. - 2469-9926. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- When atoms and molecules are ionized by laser pulses of finite duration and increasingly high intensities, the validity of the much-used dipole approximation, in which the spatial dependence and magnetic component of the external field are neglected, eventually breaks down. We report that, when going beyond the dipole approximation for the description of atoms exposed to ultraviolet light, the spatial dependence of the pulse shape, the envelope, provides the dominant correction, while the spatial dependence of the carrier is negligible. We present a first-order beyond-dipole correction to the Hamiltonian which accounts exclusively for nondipole effects stemming from the carrier envelope of the pulse. We demonstrate by ab initio calculations for hydrogen that this approximation, which we refer to as the envelope approximation, reproduces the full interaction beyond the dipole approximation for absolute and differential observables and proves to be valid for a broad range of high-frequency fields. This is done both for the Schrodinger and the Dirac equation. Moreover, it is demonstrated that the envelope approximation provides an interaction-term which gives rise to faster numerical convergence in terms of partial waves compared to its exact counterpart.
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