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FROB01 | Achieving Microfocus of the 13.5-nm FLASH Beam for Exploring Matter Under Extreme Conditions | 784 |
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We have focused a beam (BL3) of FLASH (Free-electron LASer in Hamburg: 13.5 nm, 15fs, 10μJ, 5Hz) using a fine polished off-axis parabola having a focal length of 270 mm and coated with a Mo/Si-ML giving a reflectivity of 67% at 13.5 nm. The OAP was mounted and aligned with a picomotor control six-axis gimbel. Beam imprints on PMMA were used to measure focus and the focused beam was used to create isochoric heating of various slab targets. Results show the focal spot has a diameter of <1μm producing intensities greater than 1016 Wcm−2. Observations were correlated with simulations of best focus to provide further relevant information. This focused XUV laser beam now allows us to begin exploring matter under extreme conditions. Future experimental efforts at ’4th generation’ light sources will be outlined. |
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Evidence for Position Based Electron Entanglement in Resonant Auger Electron Emission from Dissociating O2 Molecules | ||
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The proof of entanglement on the basis of the variables position and momentum was the primary suggestion by Einstein, Rosen and Podolsky to distinguish between a quantum mechanical versus a local realistic description of our world. This paper reports on an effort to realize this proposal by employing dichotomic variables g, u and f, b for position and momentum, respectively. The result is a proof of quantum mechanics as in all former, mostly photon polarization, based studies. Our experiments regarding the entanglement of these variables reveal, that Bell type measurements of spatial variables, such as position and momentum, are a transformation between two complementary representations of them, the coherent and localized representations into each other. This process emerges along a transformation angle Θ connecting the two systems which is experimentally varied by the correlation-angle of coincident electron-ion detection. |
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Studying the Secret of Life with FELs | ||
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This talk will explore the contribution that research with Free Electron Lasers (FELs) can make to the understanding of living things. Physicists can play an important part in establishing the essential characteristics of life as demonstrated by Schoedingers book "What is Life?" (1944). While there has been considerable progress in the determination of the structures of biological molecules using x-ray diffraction there has been very little progress in studying the conformational changes that are the key to understanding the mechanisms by which biological systems self-organise and maintain their functions. We lack methods of making real time observations of conformational change in proteins and exciting biological systems with the long wavelength radiation that is made available to biological systems at room temperature through the release of free energy from chemical processes. An outline will be given of the crucial role that FELs can play in this field and results will be presented on the real time observation of conformational change in proteins. |
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Saturable Absorption with VUV FEL Radiation | ||
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We report for the first time saturable absorption in the soft x-ray regime: by photoionizing L-shell core electrons we observed on a 15fs timescale a multifold increase of transmission through an aluminium foil. While saturable absorption is a phenomenon readily seen in the optical and infrared wavelengths, it has never been observed in a core electron transition due to the short lifetimes of the created excited states and the high intensities of the soft x-rays that are needed. The experiments were performed at the XUV Free Electron Laser FLASH and used record high intensities. After the FEL pulse has passed, the aluminum sample is in an exotic state where all the aluminum atoms have a L-shell hole, and the conduction band has a 9eV temperature, while the atoms are still on their crystallographic positions. Subsequently, Auger decay heats the material to Warm Dense Matter condition, at 20eV temperatures. The saturable absorption allows for a very homogeneous and efficient heating. Therefore the method is an ideal candidate to study homogeneous Warm Dense Matter, highly relevant to planetary science, astrophysics and inertial confinement fusion. |
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FROB05 | Local Infrared Microspectroscopy with 100nm Spatial Resolution and Application to Cell Imaging | 789 |
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Performing "chemical mapping" of various objects with sub-wavelength lateral resolution, by using the infrared vibrationnal signature characterizing different molecular species, is an old dream. We have recently demonstrated such a method, called AFMIR [1]. We use the photo-thermal expansion effect, detected by an atomic force microscope tip, probing the local transient deformation induced by an infrared pulsed laser tuned at a sample absorbing wavelength. This method records directly the local infrared absorption without interference due to the medium real index of refraction (i.e. sample topography and inhomogeneities) contrary to near-field optical methods. The pulsed character of the FEL, together with the small size of the AFM tip, allows a spatial resolution better than 100 nm. Local spectroscopy and imaging can be performed. We show different examples. In particular, we have imaged single viruses imbedded into a cell [2] and living cells (in water). In this case, discrimination of the cell signal against water broadband absorption is made by selecting proper modes after Fourier analysis of the AFM cantilever modes of vibration [3]. [1] A. Dazzi et al, Optics Letters, 30 (18), 2388 (2005) |
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