| 1. |
- Rohringer, N., et al.
(författare)
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Stimulated X-Ray Raman Scattering with Free-Electron Laser Sources
- 2016
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Ingår i: X-Ray Lasers 2014. - Cham : Springer. - 0930-8989. - 9783319195216 - 9783319195209 ; , s. 201-207
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Bokkapitel (refereegranskat)abstract
- Stimulated electronic x-ray Raman scattering is the building block for several proposed x-ray pump probe techniques, that would allow the study of electron dynamics at unprecedented timescales.We present high spectral resolution data on stimulated electronic x-ray Raman scattering in a gas sample of neon using a self-amplified spontaneous emission x-ray free-electron laser. Despite the limited spectral coherence and broad bandwidth of these sources, high-resolution spectra can be obtained by statistical methods, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules and the results of a recent experiment in CO are discussed.
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| 2. |
- Zhaunerchyk, Vitali, et al.
(författare)
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Disentangling formation of multiple-core holes in aminophenol molecules exposed to bright X-FEL radiation
- 2015
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 48:24
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Tidskriftsartikel (refereegranskat)abstract
- Competing multi-photon ionization processes, some leading to the formation of double core hole states, have been examined in 4-aminophenol. The experiments used the linac coherent light source (LCLS) x-ray free electron laser, in combination with a time-of-flight magnetic bottle electron spectrometer and the correlation analysis method of covariance mapping. The results imply that 4-aminophenol molecules exposed to the focused x-ray pulses of the LCLS sequentially absorb more than two x-ray photons, resulting in the formation of multiple core holes as well as in the sequential removal of photoelectrons and Auger electrons (so-called PAPA sequences).
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| 3. |
- Mucke, Melanie, et al.
(författare)
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Covariance mapping of two-photon double core hole states in C2H2 and C2H6 produced by an x-ray free electron laser
- 2015
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Few-photon ionization and relaxation processes in acetylene (C2H2) and ethane (C2H6) were investigated at the linac coherent light source x-ray free electron laser (FEL) at SLAC, Stanford using a highly efficient multi-particle correlation spectroscopy technique based on a magnetic bottle. The analysis method of covariance mapping has been applied and enhanced, allowing us to identify electron pairs associated with double core hole (DCH) production and competing multiple ionization processes including Auger decay sequences. The experimental technique and the analysis procedure are discussed in the light of earlier investigations of DCH studies carried out at the same FEL and at third generation synchrotron radiation sources. In particular, we demonstrate the capability of the covariance mapping technique to disentangle the formation of molecular DCH states which is barely feasible with conventional electron spectroscopy methods.
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| 4. |
- Zhaunerchyk, Vitali, et al.
(författare)
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Using covariance mapping to investigate the dynamics of multi-photon ionization processes of Ne atoms exposed to X-FEL pulses
- 2013
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:16, s. 164034-
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Tidskriftsartikel (refereegranskat)abstract
- We report on a detailed investigation into the electron emission processes of Ne atoms exposed to intense femtosecond x-ray pulses, provided by the Linac Coherent Light Source Free Electron Laser (FEL) at Stanford. The covariance mapping technique is applied to analyse the data, and the capability of this approach to disentangle both linear and nonlinear correlation features which may be hidden on coincidence maps of the same data set is demonstrated. Different correction techniques which enable improvements on the quality of the spectral features extracted from the covariance maps are explored. Finally, a method for deriving characteristics of the x-ray FEL pulses based on covariance mapping in combination with model simulations is presented.
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| 5. |
- Frasinski, L. J., et al.
(författare)
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Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping
- 2013
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:7, s. 073002-
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Tidskriftsartikel (refereegranskat)abstract
- When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called partial covariance mapping'' to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.
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| 6. |
- Bruns, F, et al.
(författare)
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Complementary and alternative medicine experience in radiation oncology patients : first results of a multi-center approach
- 2006
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Ingår i: Trace elements and electrolytes. - 0946-2104. ; 23:4, s. 318-325
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Tidskriftsartikel (refereegranskat)abstract
- In recent years the demand and use of complementary and alternative medicine (CAM) in malignant diseases has increased noticeably. Since the general knowledge about CAM use is scant and CAM could potentially interact with standard therapies the German Working group “Trace Elements and Electrolytes in Oncology” performed a multi-centric study to comprehensively evaluate the use of CAM therapies in cancer patients treated with radiotherapy. Methods: 1,013 patients receiving consecutively radiotherapy for malignant diseases were interviewed using a standardized questionnaire including clinical and pathological tumor parameters as well as the type of CAM and reasons for CAM use. A self-assessment of patients’ personal conditions was performed in order to evaluate the subjective impact of CAM on quality of life. Results: A total of 59% of patients reported using CAM therapies. CAM use was more common in female patients, generally higher in advanced stages of disease and most common in breast cancer patients. Most frequently reported CAM therapies were vitamins (18%), mistletoe extracts (15%), selenium (10%), and other trace element preparations (7%). Multivariate logistic regression showed age, gender, tumor type and stage, and smoking behavior to be significant predictors for CAM use. A subjective improvement in quality of life due to the use of CAM was accounted for in 30% of patients. Conclusions: More than half of patients undergoing RT for cancer are using CAM therapies. Therefore, radiation oncologists should be asking for respective obtaining information about CAM use in order to avoid harmful interactions with conventional therapies. The value and potential hazards of such combined treatments have yet to be tested in further clinical studies.
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| 7. |
- Mucke, Melanie, et al.
(författare)
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Formation and decay of core-orbital vacancies in the water molecule
- 2013
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 558, s. 82-87
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Tidskriftsartikel (refereegranskat)abstract
- Primary steps in the interaction of high energy photons with water creating multiply ionised products are examined experimentally and theoretically. Double Auger decay from a 1s-hole state populates triply ionised states between 80 and 140 eV binding energy. Ejection of one 1s electron and one valence electron gives states around 570 eV which decay to triply ionised states between 75 and 110 eV. Nuclear motion in these states competes with Auger decay and substantially modifies the final state spectra. The double core-hole state from ionisation of both 1s electrons is found at 1171 +/- 1 eV and calculated at 1170.85 eV.
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| 8. |
- Wolf, T.J.A., et al.
(författare)
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Transient Resonant Auger-Meitner Spectra of Photoexcited Thymine
- 2021
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Ingår i: Faraday discussions. - : Royal Society of Chemistry (RSC). - 1364-5498 .- 1359-6640. ; 228, s. 555-70
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Tidskriftsartikel (refereegranskat)abstract
- We present the first investigation of excited state dynamics by resonant Auger-Meitner spectroscopy (also known as resonant Auger spectroscopy) using the nucleobase thymine as an example. Thymine is photoexcited in the UV and probed with X-ray photon energies at and below the oxygen K-edge. After initial photoexcitation to a ππ* excited state, thymine is known to undergo internal conversion to an nπ* excited state with a strong resonance at the oxygen K-edge, red-shifted from the groundstate π* resonances of thymine (see our previous study Wolf et al.,Nat. Commun., 2017,8, 29). We resolve and compare the Auger-Meitner electron spectra associated both with the excited state and ground state resonances, and distinguish participato rand spectator decay contributions. Furthermore, we observe simultaneously with the decay of the nπ* state signatures the appearance of additional resonant Auger-Meitner contributions at photon energies between the nπ* state and the ground state resonances. We assign these contributions to population transfer from the nπ* state to a ππ* triplet state via intersystem crossing on the picosecond timescale based on simulations of the X-ray absorption spectra in the vibrationally hot triplet state. Moreover, we identify signatures from the initially excited ππ* singlet state which we have not observed in our previous study.
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