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The SPECIES beamline has been transferred to the new 1.5 GeV storage ring at the MAX IV Laboratory. Several improvements have been made to the beamline and its endstations during the transfer. Together the Ambient Pressure X-ray Photoelectron Spectroscopy and Resonant Inelastic X-ray Scattering endstations are capable of conducting photoelectron spectroscopy in elevated pressure regimes with enhanced time-resolution and flux and X-ray scattering experiments with improved resolution and flux. Both endstations offer a unique capability for experiments at low photon energies in the vacuum ultraviolet and soft X-ray range. In this paper, the upgrades on the endstations and current performance of the beamline are reported.

Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. A first step toward this goal is the investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser. Earlier SXRS experiments relied on signal amplification during pulse propagation through dense resonant media. By contrast, our method reveals the fundamental process in which photons from the primary radiation source directly interact with a single atom. We introduce an experimental protocol in which scattered neutral atoms rather than scattered photons are detected. We present SXRS measurements at the neon K edge and a quantitative theoretical analysis. The method should become a powerful tool in the exploration of nonlinear x-ray physics.

Resonant inelastic x-ray scattering spectra excited at the fluorine K resonances of SF(6)have been recorded. While a small but significant propensity for electronically parity-allowed transitions is found, the observation of parity-forbidden electronic transitions is attributed to vibronic coupling that breaks the global inversion symmetry of the electronic wavefunction and localizes the core hole. The dependence of the scattering cross section on the polarization of the incident radiation and the scattering angle is interpreted in terms of local pi/sigma symmetry around the S-F bond. This symmetry selectivity prevails during the dissociation that occurs during the scattering process.

Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic and molecular species. Using the seeded free electron laser FERMI and a novel detection scheme, we have revealed the two-photon excitation spectra of dipole-forbidden doubly excited states in helium. The spectral profiles of the lowest (-1,0)^{+1} ^{1}S^{e} and (0,1)^{0} ^{1}D^{e} resonances display energy shifts in the meV range that depend on the pulse intensity. The results are explained by an effective two-level model based on calculated Rabi frequencies and decay rates.

We have studied the spectral features of Cl LII,III resonant x-ray Raman scattering of HCl molecules in gas phase both experimentally and theoretically. The theory, formulated in the intermediate-coupling scheme, takes into account the spin-orbital and molecular-field splittings in the Cl 2p shells, as well as the Coulomb interaction of the core hole with unoccupied molecular orbitals. Experiment and theory display nondispersive dissociative peaks formed by decay transitions in both molecular and dissociative regions. The molecular and atomic peaks collapse in a single narrow resonance because the dissociative potentials of core-excited and final states are parallel to each other along the whole pathway of the nuclear wave packet.

The O Kalpha x-ray emission spectra of water clusters with different sizes and conformations embedded in a continuum medium are simulated. The calculations have successfully explained the experimental spectra of water in both gas and liquid phases. It is shown that the x-ray emission spectra are very sensitive to the local hydrogen bonding structures. Strong electron sharing between different water molecules is observed and its possible connection to the covalency of hydrogen bonding is discussed. The experimentally observed strong excitation energy dependence of the spectra has been interpreted in terms of the polarization and angular dependence for the gas phase, and in terms of variations of local hydrogen bonding structures for the liquid phase., QC 20100525 QC 20111031

The spin transition in LaCoO3 is investigated by temperature-dependent resonant soft X-ray emission spectroscopy near the Co 2p absorption edges. This element-specific technique is more bulk sensitive with respect to the temperature-induced spin state of the Co3+ ions in LaCoO3 than other high-energy spectroscopic methods. The spin transition is interpreted and discussed with ab initio density-functional theory within the fixed-spin moment method, which is found to yield consistent spectral functions to the experimental data. The spectral changes for LaCoO3 as a function of temperature suggest a change in spin state as the temperature is raised from 85 to 300 K, while the system remains in the same spin state as the temperature is further increased to 510 K., Original Publication:Martin Magnuson, S. M. Butorin, C. Såthe, J. Nordgren and P. Ravindran, Spin transition in LaCoO3 investigated by resonant soft X-ray emission spectroscopy, 2004, Europhysics letters, (68), 2, 289-295.http://dx.doi.org/10.1209/epl/i2004-10183-8Copyright: EDP Sciences.http://publications.edpsciences.org

The interaction of oxygen with C60 molecules was studied on a C60 film which had been exposed simultaneously to oxygen and UV-light for 190 hours, producing an approximately C60O1 stoichiometry in the bulk of the sample. C K-edge and O K-edge NEXAFS (using total fluorescence yield detection) and resonant X-ray inelastic scattering (RIXS) spectra from the sample film were measured and the C K-edge data were compared to the spectra from pristine C60 as reference. The C K-edge absorption and emission spectral profiles of the oxygen-doped sample are similar to those of the C60 reference, suggesting that cage breaking of C60 under these conditions, if any, is negligible. However, the redistribution of intensities in the spectra indicates changes in the occupancies of different molecular orbitals, possibly due to changes in electron density upon reaction. Similarities of the O K-edge soft X-ray emission (SXES) spectra to several small oxygen-containing molecules is being discussed in terms of bonding models.

Resonant soft X-ray emission spectra have been measured at the Ni 2p edge of a planar nickel complex K2Ni(CN)4·H2O and interpreted by performing ab initio configuration interaction calculations. This cyano complex shows characteristic metal-to-ligand charge transfer (MLCT) bands in the Ni 2p photoabsorption spectra. Resonant soft X-ray emission via the MLCT intermediate states can be interpreted as valence MLCT excitations within a one-electron picture. On the other hand, resonant soft X-ray emission via the intra-atomic Ni 2p–3d intermediate state corresponding to the white line excitation shows significant electron correlation effects.

Ultrathin AlAs(100) layers of 1-, 2-, and 5-ML thickness buried in GaAs are investigated by ab initio calculations. Unique experimental soft-x-ray emission spectra are explained in terms of interface effects and changes with layer thickness are found in the density of states. Only the central layer in the 5-ML geometry is bulklike. A valence-band offset of 0.53 eV is also found for this structure, while no offset exists in the 1- and 2-ML cases. Very good agreement is achieved between theory and experiment.

We show evidence of dissociation during resonant inelastic soft x-ray scattering. Carbon and oxygen K-shell and sulfur L-shell resonant and nonresonant x-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur L2,3→π*, σ* excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast the carbon and oxygen spectra show weaker line-shape variations and no atomic lines. The spectra are compared to results from ab initio calculations. The discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies., Original Publication: Martin Magnuson, J. Guo, C. Såthe, J.-E. Rubensson, J. Nordgren, P. Glans, L. Yang, P. Sałek and H. Ågren, Competition between decay and dissociation of core-excited carbonyl sulfide studied by x-ray scattering, 1999, Physical Review A. Atomic, Molecular, and Optical Physics, (59), 4281-4287. http://dx.doi.org/10.1103/PhysRevA.59.4281 Copyright: American Physical Society http://www.aps.org

Resonant inelastic scattering measurements of the conjugated polymer, poly(pyridine-2,5-diyl) have been performed at the nitrogen and carbon K-edges using synchrotron radiation. For comparison, molecular orbital calculations of the spectra have been carried out with the repeat unit as a model molecule of the polymer chain. The resonant emission spectra show depletion of the π electron bands which is consistent with symmetry selection and momentum conservation rules. The depletion is most obvious in the resonant inelastic scattering spectra of carbon while the nitrogen spectra are dominated by lone pair n orbital emission of σ symmetry and are less excitation energy dependent. By comparing the measurements to calculations an isomeric dependence of the resonant spectra is found giving preference to two of the four possible isomers in the polymer.

The electronic structure of the conjugated polymer, polyaniline, has been studied by resonant and nonresonant soft x-ray emission spectroscopy using synchrotron radiation for the excitation. The measurements were made on polyaniline and a few doped (protonated) phases for both the carbon and nitrogen contents. The resonant x-ray emission spectra show depletion of the π electron bands due to the selective excitation which enhances the effect of symmetry selection rules. The valence band structures in the x-ray emission spectra attributed to the π bands show unambiguous changes of the electronic structure upon protonation. By comparing to x-ray absorption measurements, the chemical bonding and electronic configuration is characterized.

We show evidence of dissociation during resonant inelastic soft x-ray scattering Carbon and oxygen K-shell and sulfur L-shell resonant and nonresonant x-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur L-2,L-3-->pi*, sigma* excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast thr carbon and oxygen spectra show weaker line-shape variations and no atomic Lines. The spectra are compared to results from ab initio calculations. The discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies.

Soft x-ray-emission spectroscopy is applied to measure the amount of dynamic symmetry breaking in core-excited acetylene, ethylene, and ethane. Large variations are observed between the molecules and are rationalized in terms of the different C-C bond lengths: Shorter bond lengths give smaller symmetry breaking. The results also indicate that asymmetric modes are important for all the systems studied, in contradiction to previous assumptions in literature.