Conny Såthe

Ground state potential energy surfaces around selected atoms from resonant inelastic x-ray scattering.

Thermally driven chemistry as well as materials’ functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.

The SPECIES beamline at the MAX IV Laboratory: A facility for soft X-ray RIXS and APXPS

SPECIES, the soft X-ray beamline for resonant inelastic scattering and ambient-pressure photoelectron spectroscopy at MAX IV, is described.

Auger electron and photoabsorption spectra of glycine in the vicinity of the oxygen K-edge measured with an X-FEL

We report the first measurement of the near oxygen K-edge auger spectrum of the glycine molecule. Our work employed an x-ray free electron laser as the photon source operated with input photon energies tunable between 527 and 547 eV. Complete electron spectra were recorded at each photon energy in the tuning range, revealing resonant and non-resonant auger structures. Finally ab initio theoretical predictions are compared with the measured above the edge auger spectrum and an assignment of auger decay channels is performed.

Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

A. Sanchez-Gonzalez,1 P. Micaelli,1 C. Olivier,1 T. R. Barillot,1 M. Ilchen,2, 3 A. A. Lutman,4 A. Marinelli,4 T. Maxwell,4 A. Achner,3 M. Agåker,5 N. Berrah,6 C. Bostedt,4, 7 J. Buck,8 P. H. Bucksbaum,2, 9 S. Carron Montero,4, 10 B. Cooper,1 J. P. Cryan,2 M. Dong,5 R. Feifel,11 L. J. Frasinski,1 H. Fukuzawa,12 A. Galler,3 G. Hartmann,8, 13 N. Hartmann,4 W. Helml,4, 14 A. S. Johnson,1 A. Knie,13 A. O. Lindahl,2, 11 J. Liu,3 K. Motomura,12 M. Mucke,5 C. O’Grady,4 J-E. Rubensson,5 E. R. Simpson,1 R. J. Squibb,11 C. Såthe,15 K. Ueda,12 M. Vacher,16, 17 D. J. Walke,1 V. Zhaunerchyk,11 R. N. Coffee,4 and J. P. Marangos1 1Department of Physics, Imperial College, London, SW7 2AZ, United Kingdom 2Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA 3European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany 4Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA 5Department of Physics and Astronomy, Uppsala University, Uppsala, 75120, Sweden 6Department of Physics, University of Connecticut, 2152 Hillside Road, U-3046, Storrs, CT 06269, USA 7Argonne National Laboratory, Lemont, IL 60439, USA 8Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, Hamburg, 22607, Germany 9Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, CA 94305, USA 10California Lutheran University, 60 W Olsen Rd, Thousand Oaks, CA 91360, USA 11Department of Physics, University of Gothenburg, Origovägen 6B, 41296 Gothenburg, Sweden 12Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan 13Institut für Physik und CINSaT, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany 14Physics Department, TU Munich, James-Franck-Str. 1, 85748 Garching, Germany 15MAX IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden 16Department of Chemistry, Imperial College London, London SW7 2AZ, United Kingdom 17Department of Chemistry Ångtröm, Uppsala University, Uppsala, 75120, SwedenFree-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy, we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. This opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.

Resonant Mn L emission spectra of layered manganite La1.2Sr1.8Mn2O7

Resonant Mn L α,β soft X-ray emission spectra of a colossal magnetoresistive manganese oxide La 1.2 Sr 1.8 Mn 2 O 7 have been measured at the Mn L 2,3 -edges excited by monochromatized undulator radiation. The excitation energy dependence of the spectra has been analyzed in terms of d – d and charge-transfer excitations. The experimental spectra are reproduced by the multiplet calculation for the Mn 3+ configuration, which is consistent with the dominant occupancy of the 3 d x 2 - y 2 orbital and probably a phase separation.

Anomalously strong two-electron one-photon X-ray decay transitions in CO caused by avoided crossing.

The unique opportunity to study and control electron-nuclear quantum dynamics in coupled potentials offered by the resonant inelastic X-ray scattering (RIXS) technique is utilized to unravel an anomalously strong two-electron one-photon transition from core-excited to Rydberg final states in the CO molecule. High-resolution RIXS measurements of CO in the energy region of 12–14 eV are presented and analyzed by means of quantum simulations using the wave packet propagation formalism and ab initio calculations of potential energy curves and transition dipole moments. The very good overall agreement between the experimental results and the theoretical predictions allows an in-depth interpretation of the salient spectral features in terms of Coulomb mixing of “dark” with “bright” final states leading to an effective two-electron one-photon transition. The present work illustrates that the improved spectral resolution of RIXS spectra achievable today may call for more advanced theories than what has been used in the past.

Motion control system of MAX IV Laboratory soft x-ray beamlines

At the MAX IV Laboratory, five new soft x-ray beamlines are under development. The first is Species and it will be used to develop and set the standard of the control system, which will be common across the facility. All motion axes at MAX IV will be motorized using stepper motors steered by the IcePAP motion controller and a mixture of absolute and incremental encoders following a predefined coordinate system. The control system software is built in Tango and uses the Python-based Sardana framework. The user controls the entire beamline through a synoptic overview and Sardana is used to run the scans.

Resonant and nonresonant x-ray emission spectroscopy of poly(pyridine-2,5-diyl)

The Advanced Light Source (ALS), a national user facility located at Ernest Orlando Lawrence Berkeley National Laboratory of the University of California is available to researchers from academia, industry, and government laboratories. Operation of the ALS is funded by the Department of Energys Office of Basic Energy Sciences. This Compendium contains abstracts written by users summarizing research completed or in progress during 1997, ALS technical reports describing ongoing efforts related to improvement in machine operations and research and development projects, and information on ALS beamlines planned through 1998.Organic conjugated polymers have the electronic structure of semiconductors and can be doped to become good conductors (1). Conjugated polymers are now used as active materials in a wide variety of ...Conjugated polymers have been the subject of much interest owing to their unique electronic properties which can be technically exploited e.g., as doping induced electrical conductors and light emi ...