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| 2. |
- Kimberg, V., et al.
(författare)
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Single-Molecule X-Ray Interferometry : Controlling Coupled Electron-Nuclear Quantum Dynamics and Imaging Molecular Potentials by Ultrahigh-Resolution Resonant Photoemission and Ab Initio Calculations
- 2013
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Ingår i: Physical Review X. - : American Physical Society. - 2160-3308. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports an advanced study of the excited ionic states of the gas-phase nitrogen molecule in the binding-energy region of 22-34 eV, combining ultrahigh-resolution resonant photoemission (RPE) and ab initio configuration-interaction calculations. The RPE spectra are recorded for nine photon energies within the N 1s -> pi* absorption resonance of N-2 by using a photon bandwidth that is considerably smaller than lifetime broadening, and the dependence on excitation energy of the decay spectra is analyzed and used for the first assignment of 12 highly overlapped molecular states. The effect on the RPE profile of avoided curve crossings between the final N-2(+) ionic states is discussed, based on theoretical simulations that account for vibronic coupling, and compared with the experimental data. By use of synchrotron radiation with high spectral brightness, it is possible to selectively promote the molecule to highly excited vibrational sublevels of a core-excited electronic state, thereby controlling the spatial distribution of the vibrational wave packets, and to accurately image the ionic molecular potentials. In addition, the mapping of the vibrational wave functions of the core-excited states using the bound final states with far-from-equilibrium bond lengths has been achieved experimentally for the first time. Theoretical analysis has revealed the rich femtosecond nuclear dynamics underlying the mapping phenomenon. DOI: 10.1103/PhysRevX.3.011017
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| 3. |
- Lindblad, Andreas, et al.
(författare)
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Vibrational scattering anisotropy in O-2-dynamics beyond the Born-Oppenheimer approximation
- 2012
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14, s. 113018-
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Tidskriftsartikel (refereegranskat)abstract
- Born-Oppenheimer and Franck-Condon approximations are two major concepts in the interpretation of electronic excitations and modeling of spectroscopic data in the gas and condensed phases. We report large variations of the anisotropy parameter (beta) for the fully resolved vibrational sub-states of the X-2 Pi(g) electronic ground state of O-2(+) populated by participator resonant Auger decay following excitations of K-shell electrons into the sigma(star) resonance by monochromatic x-rays. Decay spectra for light polarization directions parallel and perpendicular to the electron detection axis recorded at four different excitation energies in the vicinity of the O 1s -> sigma(star) transition are presented. Breakdown of the Born-Oppenheimer approximation is for the first time selectively observed for the lower vibrational sub-states, where two quantum paths-resonant and direct-leading to the same final cationic state exist. The higher vibrational sub-states can only be populated by resonant photoemission; hence no interference between these channels can occur.
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| 4. |
- Carniato, Stéphane, et al.
(författare)
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Resonant X-ray Raman scattering on molecules : A benchmark study on HCl
- 2010
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 181:2-3, s. 116-120
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Tidskriftsartikel (refereegranskat)abstract
- Resonant X-ray Raman scattering is a powerful tool to study molecular dynamics and subtle chemical effects like the molecular field beyond vibrational and lifetime limitations. Using this technique in the tender X-ray region, gas phase HCl is studied as a benchmark molecule for other compounds like freons, which play an important role in physical-chemical properties of the ozone layer of atmosphere.
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| 5. |
- Carniato, S., et al.
(författare)
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Thomson-resonant interference effects in elastic x-ray scattering near the Cl K edge of HCl
- 2012
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:9, s. 094311-
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally observed interference effects in elastic x-ray scattering from gas-phase HCl in the vicinity of the Cl Kedge. Comparison to theory identifies these effects as interference effects between non-resonant elastic Thomson scattering and resonant Raman scattering. The results indicate the non-resonant Thomson and resonant Raman contributions are of comparable strength. The measurements also exhibit strong polarization dependence, allowing an easy identification of the resonant and non-resonant contributions.
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| 6. |
- Miao, Quan, et al.
(författare)
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Dissociative X-ray Lasing
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:23, s. 233905-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray lasing is predicted to ensue when molecules are pumped into dissociative core-excited states by a free-electron-laser pulse. The lasing is due to the population inversion created in the neutral dissociation product, and the process features self-trapping of the x-ray pulse at the gain ridge. Simulations performed for the HCl molecule pumped at the 2p(1/2) -> 6 sigma resonance demonstrate that the scheme can be used to create ultrashort coherent x-ray pulses.
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| 7. |
- Wang, Teng, et al.
(författare)
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The influence of feedback with different opinions on continued user participation in online newsgroups
- 2013
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Ingår i: Proceedings of the 2013 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining, ASONAM 2013. - New York, NY, USA : IEEE Computer Society. - 9781450322409 ; , s. 388-395
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Konferensbidrag (refereegranskat)abstract
- With the popularity of social media in recent years, it has been a critical topic for social network designer to understand the factors that influence continued user participation in online newsgroups. Our study examines how feedback with different opinions is associated with participants' lifetime in online newsgroups. Firstly, we propose a new method of classifying different opinions among user interaction contents. Generally, we leverage user behavior information in online newsgroups to estimate their opinions and evaluate our classification results based on linguistic features. In addition, we also implement this opinion classification method into our SINCERE system as a real-time service. Based on this opinion classification tool, we use survival analysis to examine how others' feedback with different opinions influence continued participation. In our experiment, we analyze more than 88,770 interactions on the official Occupy LA Facebook page. Our final result shows that not only the feedback with the same opinions as the user, but also the feedback with different opinions can motivate continued user participation in online newsgroup. Furthermore, an interaction of feedback with both the same and different opinions can boost user continued participation to the greatest extent. This finding forms the basis of understanding how to improve online service in social media. Copyright 2013 ACM.
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