| 1. |
- Cryan, James P., et al.
(författare)
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Auger Electron Angular Distribution of Double Core-Hole States in the Molecular Reference Frame
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:8, s. 083004-
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Tidskriftsartikel (refereegranskat)abstract
- The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×1011 photons in a ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.
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| 2. |
- Elshakre, M., et al.
(författare)
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A photoelectron and double photoionization study of the valence electronic structure of 1,4-bromofluorobenzene
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:18, s. 184302-
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Tidskriftsartikel (refereegranskat)abstract
- Conventional photoelectron and time-of-flight photoelectron-photoelectron coincidence (TOF-PEPECO) spectra have been measured for the outer valence region of the 1,4-bromofluorobenzene molecule. The photoelectron spectra were recorded using Hela radiation from a resonance Source, and the TOF-PEPECO spectra were recorded using HeII alpha radiation from a pulsed resonance source. The former provide energies of the cationic states and the latter of the dicationic states. The spectra are adequately interpreted with the aid of accurate Green's function calculations, showing very significant correlation effects. The lowest double ionization energy is found at 23.45 eV associated with the (4b(1))X-2 (1)A(1) dicationic state.
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| 3. |
- Linusson, Per, et al.
(författare)
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Double photoionization of thiophene and bromine-substituted thiophenes
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:23, s. 234303-
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Tidskriftsartikel (refereegranskat)abstract
- We report the double photoionization spectra of thiophene, 3-bromothiophene, and 3,4-dibromothiophene using a coincidence spectroscopy technique based on electron time-of-flight measurements. Spectra have been recorded between the onset and 40.814 eV using He II alpha radiation. The He I photoelectron spectrum of 3,4-dibromothiophene has also been measured. All the spectra have been analyzed and interpreted in detail on the basis of theoretical simulations from accurate Green's function calculations.
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| 4. |
- Fang, L., et al.
(författare)
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Multiple Ionization and Double Core-hole Production in Molecules using the LCLS X-ray FEL
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:3, s. 032028-
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Tidskriftsartikel (refereegranskat)abstract
- We used the world's first hard x-ray FEL to investigate the response of molecular systems to the ultra-intense, femtosecond x-ray radiation. We report sequential multiphoton ionization, frustrated absorption and double core hole production mechanisms.
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| 5. |
- Farrell, J. P., et al.
(författare)
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Ultrafast X-ray probe of nucleobase photoprotection
- 2012
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Ingår i: Quantum Electronics and Laser Science Conference. - 9781467318396 ; , s. 6327153-
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Konferensbidrag (refereegranskat)abstract
- We will present first results of a UV-pump X-ray-probe study of the photoprotection mechanism of thymine. The experiment used element specific Auger spectroscopy and was carried out at the LCLS.
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| 6. |
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| 7. |
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| 8. |
- Kolorenc, P., et al.
(författare)
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Three-electron collective Auger decay in CH3F
- 2015
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- We report on experimental and theoretical study of collective Auger decay of double inner-valence vacancy in fluoromethane, in which two electrons simultaneously fill the vacancies and a third electron is ejected to continuum. Calculations predict the respective lifetime of the double vacancy state to be in the femtosecond range, typical for two-electron Auger decay. Measured electron spectra indirectly support this rather surprising result.
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| 9. |
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| 10. |
- McFarland, B. K., et al.
(författare)
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Probing nucleobase photoprotection with soft x-rays
- 2013
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Ingår i: XVIIITH INTERNATIONAL CONFERENCE ON ULTRAFAST PHENOMENA. - : EDP Sciences. - 9782759809561 ; , s. 07004-
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Konferensbidrag (refereegranskat)abstract
- Nucleobases absorb strongly in the ultraviolet region, leading to molecular excitation into reactive states. The molecules avoid the photoreactions by funnelling the electronic energy into less reactive states on an ultrafast timescale via non-Born-Oppenheimer dynamics. Current theory on the nucleobase thymine discusses two conflicting pathways for the photoprotective dynamics. We present our first results of our free electron laser based UV-pump soft x-ray-probe study of the photoprotection mechanism of thymine. We use the high spatial sensitivity of the Auger electrons emitted after the soft x-ray pulse induced core ionization. Our transient spetra show two timescales on the order of 200 fs and 5 ps, in agreement with previous (all UV) ultrafast experiments. The timescales appear at different Auger kinetic energies which will help us to decipher the molecular dynamics.
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