| 1. |
- Feifel, R., et al.
(författare)
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Role of stray light in the formation of high-resolution resonant photoelectron spectra : an experimental and theoretical study of N-2
- 2004
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 134:1, s. 49-65
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Tidskriftsartikel (refereegranskat)abstract
- We show that the undular stray light, diffusely scattered by the optical system of a synchrotron beamline, can play an important role in the formation of high-resolution resonant photoelectron (RPE) spectra. The influence of the stray light is mediated through the Stokes doubling effect, with the Lorentzian tail of the spectral function being replaced by a more complicated form. This effect is shown to appear in the high-resolution resonant photoelectron spectrum of the N-2 molecule in which the spectral shape of the non-Raman (NR) bands differs qualitatively for the A(2)Pi(u) and X(2)Sigma(g)(+) final states. A particularly large enhancement of the non-Raman Stokes line is observed for the A-state while the picture is inverted for the X-state where the non-Raman band is suppressed. It is shown that the resonant photoemission profile is affected by two qualitatively different detunings, the detuning of the monochromatized line relative to the photoabsorption line and the detuning of the undulator harmonic relative to the same reference line. The experimental data show that the relative intensity of the non-Raman line strongly depends on the tuning of the undulator harmonic with respect to the selected monochromator bandpass, leading to a strong decrease of the Stokes line intensity for certain undulator detunings. A clear red-shift asymmetry for the decrease in the Stokes line intensity is observed when the monochromator line is detuned towards negative photon frequencies, whereas the picture is reverted for the situation of a positively detuned monochromator line. The results show the necessity to control the stray light and to investigate both the Raman and non-Raman contributions to the spectral profiles in order to avoid misinterpretation and in order to make full use of the information available in resonant photoemission spectra of molecules.
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| 2. |
- Feifel, R., et al.
(författare)
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Generalization of the duration-time concept for interpreting high-resolution resonant photoemission spectra
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 69:2, s. 022707-
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Tidskriftsartikel (refereegranskat)abstract
- The duration-time concept, vastly successful for interpreting the frequency dependence of resonant radiative and nonradiative x-ray scattering spectra, is tested for fine-scale features that can be obtained with state of the art high-resolution spectroscopy. For that purpose resonant photoelectron (RPE) spectra of the first three outermost singly ionized valence states X (2)Sigma(g)(+), A (2)Pi(u), and B (2)Sigma(u)(+), are measured for selective excitations to different vibrational levels (up to n=13) of the N 1s-->pi(*) photoabsorption resonance in N-2 and for negative photon frequency detuning relative to the adiabatic 0-0 transition of this resonance. It is found that different parts of the RPE spectrum converge to the spectral profile of direct photoionization (fast scattering) for different detunings, and that the RPE profiles are asymmetrical as a function of frequency detuning. The observed asymmetry contradicts the picture based on the simplified notation of a common scattering duration time, but is shown to agree with the here elaborated concept of partial and mean duration times. Results of the measurements and the simulations show that the duration time of the scattering process varies for different final electronic and different final vibrational states. This owes to two physical reasons: one is the competition between the fast vertical and the slow resonant scattering channels and the other is the slowing down of the scattering process near the zeros of the real part of the scattering amplitude.
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| 3. |
- Maxwell, Christopher A., et al.
(författare)
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Interplay between BRCA1 and RHAMM Regulates Epithelial Apicobasal Polarization and May Influence Risk of Breast Cancer
- 2011
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Ingår i: PLoS Biology. - : Public Library of Science (PLoS). - 1545-7885 .- 1544-9173. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Differentiated mammary epithelium shows apicobasal polarity, and loss of tissue organization is an early hallmark of breast carcinogenesis. In BRCA1 mutation carriers, accumulation of stem and progenitor cells in normal breast tissue and increased risk of developing tumors of basal-like type suggest that BRCA1 regulates stem/progenitor cell proliferation and differentiation. However, the function of BRCA1 in this process and its link to carcinogenesis remain unknown. Here we depict a molecular mechanism involving BRCA1 and RHAMM that regulates apicobasal polarity and, when perturbed, may increase risk of breast cancer. Starting from complementary genetic analyses across families and populations, we identified common genetic variation at the low-penetrance susceptibility HMMR locus (encoding for RHAMM) that modifies breast cancer risk among BRCA1, but probably not BRCA2, mutation carriers: n = 7,584, weighted hazard ratio ((w)HR) = 1.09 (95% CI 1.02-1.16), p(trend) = 0.017; and n = 3,965, (w)HR = 1.04 (95% CI 0.94-1.16), p(trend) = 0.43; respectively. Subsequently, studies of MCF10A apicobasal polarization revealed a central role for BRCA1 and RHAMM, together with AURKA and TPX2, in essential reorganization of microtubules. Mechanistically, reorganization is facilitated by BRCA1 and impaired by AURKA, which is regulated by negative feedback involving RHAMM and TPX2. Taken together, our data provide fundamental insight into apicobasal polarization through BRCA1 function, which may explain the expanded cell subsets and characteristic tumor type accompanying BRCA1 mutation, while also linking this process to sporadic breast cancer through perturbation of HMMR/RHAMM.
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| 4. |
- Feifel, R., et al.
(författare)
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Profile of resonant photoelectron spectra versus the spectral function width and photon frequency detuning
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 70:3
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Tidskriftsartikel (refereegranskat)abstract
- The outermost, singly ionized valence state of N-2, the X (2)Sigma(g)(+) state, is investigated in detail as a function of the photon frequency bandwidth for core excitation to the N 1s-->pi(*) resonance, where the photon frequency is tuned in between the first two vibrational levels of this bound intermediate electronic state. We find a strong, nontrivial dependence of the resulting resonant photoemission spectral profile on the monochromator function width and the frequency of its peak position. For narrow bandwidth excitation we observe a well resolved vibrational fine structure in the final electron spectrum, which for somewhat broader bandwidths gets smeared out into a continuous structure. For even broader monochromator bandwidths, it converts again into a well resolved vibrational progression. In addition, spectral features appearing below the adiabatic transition energy of the ground state of N-2(+) are observed for broadband excitation. A model taking into account the interplay of the partial scattering cross section with the spectral function is presented and applied to the X (2)Sigma(g)(+) final state of N-2(+).
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| 5. |
- Fukuzawa, Hironobu, et al.
(författare)
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Real-time observation of X-ray-induced intramolecular and interatomic electronic decay in CH2I2
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The increasing availability of X-ray free-electron lasers (XFELs) has catalyzed the development of single-object structural determination and of structural dynamics tracking in real-time. Disentangling the molecular-level reactions triggered by the interaction with an XFEL pulse is a fundamental step towards developing such applications. Here we report real-time observations of XFEL-induced electronic decay via short-lived transient electronic states in the diiodomethane molecule, using a femtosecond near-infrared probe laser. We determine the lifetimes of the transient states populated during the XFEL-induced Auger cascades and find that multiply charged iodine ions are issued from short-lived (∼20 fs) transient states, whereas the singly charged ones originate from significantly longer-lived states (∼100 fs). We identify the mechanisms behind these different time scales: contrary to the short-lived transient states which relax by molecular Auger decay, the long-lived ones decay by an interatomic Coulombic decay between two iodine atoms, during the molecular fragmentation. © 2019, The Author(s).
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