| 1. |
- Iablonskyi, D., et al.
(författare)
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Interatomic Coulombic Decay Processes after Multiple Valence Excitations in Ne Clusters
- 2015
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596 .- 1742-6588. ; 635, s. 112067-112067
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Konferensbidrag (refereegranskat)abstract
- We present a comprehensive analysis of autoionization processes in Ne clusters (similar to 5000 atoms) after multiple valence excitations by free electron laser radiation. The evolution from 2-body interatomic Coulombic decay (ICD) to 3-body ICD is demonstrated when changing from surface to bulk Frenkel exciton excitation. Super Coster-Kronig type 2-body ICD is observed at Wannier exciton which quenches the main ICD channel.
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| 2. |
- Iablonskyi, D., et al.
(författare)
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Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters
- 2016
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Ingår i: Physical Review Letters. - 0031-9007. ; 117:27
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Tidskriftsartikel (refereegranskat)abstract
- Ne clusters (∼5000 atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.
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| 3. |
- Takanashi, T, et al.
(författare)
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Time-Resolved Measurement of Interatomic Coulombic Decay Induced by Two-Photon Double Excitation of Ne2
- 2017
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Ingår i: Physical Review Letters. - 0031-9007. ; 118:3
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Tidskriftsartikel (refereegranskat)abstract
- The hitherto unexplored two-photon doubly excited states [Ne∗(2p-13s)]2 were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne2+ ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly excited states, 390(-130/+450) fs, and of the short-lived ones, less than 150 fs, are in good agreement with ab initio quantum mechanical calculations.
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| 4. |
- Alagia, M, et al.
(författare)
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Angular effects in autoionization of 3 P doubly excited states in He
- 2009
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Ingår i: Journal of Physics: Conference Series. ; 194
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Tidskriftsartikel (refereegranskat)abstract
- The first members of dipole allowed 3 P o doubly excited series in helium have been observed in resonant photoexcitation of 1 s 2 s 3 S e metastable atoms. A good agreement measured relative photoionization cross sections is achieved when theory includes the radiation damping and, also important, the effects of spin-orbit multiplet splitting on electron angular distribution.
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| 5. |
- Alagia, M., et al.
(författare)
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Excitation of 1S and 3S Metastable Helium Atoms to Doubly Excited States
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:15, s. 153001-
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Tidskriftsartikel (refereegranskat)abstract
- We present spectra of triplet and singlet metastable helium atoms resonantly photoexcited to doubly excited states. The first members of three dipole-allowed 1,3Po series have been observed and their relative photoionization cross sections determined, both in the triplet (from 1s2s 3Se) and singlet (from 1s2s 1Se) manifolds. The intensity ratios are drastically different with respect to transitions from the ground state. When radiation damping is included the results for the singlets are in agreement with theory, while for triplets spin-orbit interaction must also be taken into account.
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| 6. |
- Soderstrom, J, et al.
(författare)
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X-ray-emission-threshold-electron coincidence spectroscopy
- 2004
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 141:2-3, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- Using a penetration-field threshold photoelectron (TPE) analyzer and efficient photon detectors X-ray-emission-threshold-electron coincidence (XETECO) spectroscopy has been developed to a point where peak shape analysis becomes meaningful. The spectra can, on the present level of accuracy, be interpreted as conventional TPE spectra free from post collision interaction effects. For the neon atom and the nitrogen molecule we find a detailed correspondence with state-of-the-art photoemission spectra, both regarding peak positions, line shapes, and relative intensities. Intensity redistribution due to fast core vacancy rearrangement processes in systems with close-lying core levels, like O-2, N2O, and NO is briefly discussed. It is demonstrated that even the complex threshold behavior at the F K threshold in SF6 leads to a well-defined XETECO peak, directly corresponding to classical photoemission results. (C) 2004 Elsevier B.V. All rights reserved.
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| 7. |
- Alagia, M., et al.
(författare)
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Probing the potential energy surface by highresolution x-ray absorption spectroscopy : The umbrella motion of the coreexcited CH3 free radical
- 2007
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Ingår i: Physical Review. A. - 1050-2947 .- 1094-1622. ; 76:2, s. 124305-
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Tidskriftsartikel (refereegranskat)abstract
- A detailed study of the umbrellalike vibration in inner-shell spectroscopy is presented. The high-resolution x-ray absorption spectrum for the lowest lying core excitation of the CH3 free radical was recorded. High quality potential energy surfaces (PES) for the initial and final states of the transition were calculated as a function of the symmetrical stretching and the umbrella deformation coordinates. The strong anharmonicity along the umbrella coordinate in the double-well region of the PES of the core excited state has a strong effect on the bending vibrational progressions. The excellent agreement between the experiment and theory allows an accurate spectroscopic characterization of the vibrational structure of the electronic transition, and the estimation of the umbrella inversion time of 149 fs.
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| 8. |
- Ekström, Ulf, et al.
(författare)
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The umbrella motion of core-excited CH3 and CD3 methyl radicals
- 2008
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Ingår i: Journal of Chemical Physics. - College Park, MD United States : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 128:4, s. 044302-1-044302-11
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Tidskriftsartikel (refereegranskat)abstract
- An accurate experimental and theoretical study of the lowest core excitationof CH3 and CD3 methyl radicals is presented. The complexvibrational structure of the lowest band of the x-ray absorptionspectrum (XAS) is due to the large variation of themolecular geometry, which is planar in the ground state andpyramidal in the core-excited state. The XAS spectra of thetwo radicals were recorded at high resolution and assigned bytheoretical simulations of the spectra, taking into account the couplingof symmetrical stretching and symmetrical bending (umbrellalike) deformations of theradicals. An excellent agreement between experimental and theoretical spectral profilesallowed us to accurately characterize the vibrational structure of theelectronic transition. The similarities, as well as the differences, ofthe peculiar vibrational progression observed for the two radicals areexplained by the strong anharmonicity along the umbrella coordinate andby the isotopic variation, leading to a different probing ofthe double-well potential energy surface of the core excited stateduring the nuclear motion.
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| 9. |
- Gorczyca, TW, et al.
(författare)
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Radiative and relativistic effects in the decay of highly excited states in helium
- 2000
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Ingår i: PHYSICAL REVIEW LETTERS. - : AMERICAN PHYSICAL SOC. - 0031-9007. ; 85:6, s. 1202-1205
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Tidskriftsartikel (refereegranskat)abstract
- A recent experimental study [J.-E. Rubensson et al., Phys. Rev. Lett. 83, 947 (1999)] measured a significant fluorescence yield of the He(2lnl') photoexcited resonances, showing major qualitative differences from nonrelativistic predictions. We present a
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| 10. |
- Rubensson, Jan-Erik, et al.
(författare)
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Influence of the Radiative Decay on the Cross Section for Double Excitations in Helium
- 1999
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 83:5, s. 947-950
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Tidskriftsartikel (refereegranskat)abstract
- The fluorescence yield spectrum of the double excitations in helium has been measured. All three Rydberg series converging to the N = 2 threshold are resolved, and the intensity of the individual lines is determined. The intensity variation through each series indicates that the radiative decay channel cannot be neglected when discussing the double excitations in helium. This calls for a revision of the interpretation of the absorption spectrum, and sets the limit for using the ion yield method to monitor the absorption probability.
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