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Physical review / A 99(6), 063401 (2019). doi:10.1103/PhysRevA.99.063401, Photoprocesses of the endohedral fullerene ions Sc$_3$N@C$_{80}^+$ and Sc$_3$N@C$_{80}^-$ in the gas phase have been investigated in the photon energy ranges 30--50 eV and 280--420 eV. Single and double ionization as well as single ionization accompanied by the release of a C$_2$ dimer were observed as a function of the photon energy for the positive parent ion and double detachment was measured for the negative parent ion. The emphasis of the experiments was on the specific effects of the encapsulated trimetallic nitride cluster Sc$_3$N on the observed reactions. Clear evidence of photoexcitation near the Sc L edge is obtained with the dominating contributions visible in the one- and two-electron-removal channels. K-vacancy production in the encapsulated central nitrogen atom is seen in the single ionization of Sc$_3$N@C$_{80}^+$ but is much less pronounced in the photoionization-with-fragmentation channel. Comparison of the cross sections near the carbon K edge with the corresponding channels measured previously in the photoionization of Lu$_3$N@C$_{80}^+$ reveal strong similarities. Previously predicted sharp resonance features in the ionization of Sc$_3$N@C$_{80}^+$ ions below the Sc M edge are not confirmed. The experiments are accompanied by quantum-chemistry calculations in the Hartree-Fock approximation and by model calculations employing density functional theory (DFT)., Published by AIP, Woodbury, NY

© 2018 The Author(s). The original version of this Article contained an error in the fifth sentence of the first paragraph of the 'Application on H2' section of the Results, which incorrectly read 'The role of electron correlation is quite apparent in this presentation: Fig. 1a is empty for the uncorrelated Hartree-Fock wave function, since projection of the latter wave function onto the 2pσuorbital is exactly zero, while this is not the case for the fully correlated wave function (Fig. 1d); also, Fig. 1b, c for the uncorrelated description are identical, while Fig. 1e, f for the correlated case are significantly different.' The correct version replaces 'Fig. 1e, f' with 'Fig. 2e and f'. This has been corrected in both the PDF and HTML versions of the Article.

© 2018 American Physical Society. In a joint experimental and theoretical endeavor, photoionization of metastable C4+(1s2sS13) ions via intermediate levels with hollow, double-K-vacancy configurations 2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s, and 2p4d has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25 800 which is sufficient to separate the leading fine-structure components of the 2s2pP3 term. Many-body perturbation theory was employed to determine level-to-level cross sections for K-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. Their uncertainties are estimated to be below ±1 meV. Detailed balance confirms the present photoionization cross-section results by comparison with previous dielectronic-recombination measurements. The high accuracy of the theoretical transition energies together with the present experimental results qualify photoabsorption resonances in heliumlike ions as new, greatly improved energy-reference standards at synchrotron radiation facilities.

In a joint experimental and theoretical endeavor, photoionization of metastable $C^{4+}$($1s\,2s\; ^3S_ 1)$ ions via intermediate levels with hollow, double-K-vacancy configurations $2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s$, and $2p4d$ has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25 800 which is sufficient to separate the leading fine-structure components of the $2s2p^{3}P$ term. Many-body perturbation theory was employed to determine level-to-level cross sections for $K$-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. Their uncertainties are estimated to be below $±1$ meV. Detailed balance confirms the present photoionization cross-section results by comparison with previous dielectronic-recombination measurements. The high accuracy of the theoretical transition energies together with the present experimental results qualify photoabsorption resonances in heliumlike ions as new, greatly improved energy-reference standards at synchrotron radiation facilities.

In a joint experimental and theoretical endeavor, photoionization of metastable C4+(1s2sS13) ions via intermediate levels with hollow, double-K-vacancy configurations 2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s, and 2p4d has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25 800 which is sufficient to separate the leading fine-structure components of the 2s2pP3 term. Many-body perturbation theory was employed to determine level-to-level cross sections for K-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. Their uncertainties are estimated to be below ±1 meV. Detailed balance confirms the present photoionization cross-section results by comparison with previous dielectronic-recombination measurements. The high accuracy of the theoretical transition energies together with the present experimental results qualify photoabsorption resonances in heliumlike ions as new, greatly improved energy-reference standards at synchrotron radiation facilities.

Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten, SNI 2018, Garching, Germany, 17 Sep 2018 - 19 Sep 2018

© 2017. The American Astronomical Society. All rights reserved.. Single, double, and triple photoionization of Ne+ ions by single photons have been investigated at the synchrotron radiation source PETRA III in Hamburg, Germany. Absolute cross-sections were measured by employing the photon-ion merged-beams technique. Photon energies were between about 840 and 930 eV, covering the range from the lowest-energy resonances associated with the excitation of one single K-shell electron up to double excitations involving one K- and one L-shell electron, well beyond the K-shell ionization threshold. Also, photoionization of neutral Ne was investigated just below the K edge. The chosen photon energy bandwidths were between 32 and 500 meV, facilitating the determination of natural line widths. The uncertainty of the energy scale is estimated to be 0.2 eV. For comparison with existing theoretical calculations, astrophysically relevant photoabsorption cross-sections were inferred by summing the measured partial ionization channels. Discussion of the observed resonances in the different final ionization channels reveals the presence of complex Auger-decay mechanisms. The ejection of three electrons from the lowest K-shell-excited Ne+() level, for example, requires cooperative interaction of at least four electrons.

Cross sections for photoionization and photofragmentation of singly, doubly and triply charged Lu3N@C80 ions have been measured using the photon-ion merged-beams technique at the PETRA III synchrotron light source. The measured spectra exhibit prominent resonance features at energies around the carbon K edge. In contrast to that, no signatures of the nitogen K and lutetium M edges have been found in the experimentally investigated reaction channels.

The multiple ionisation of atomic Mn, excited at (photon energy: 52.1 eV) and above (photon energy: 61.1 eV) the discrete giant 3p���3d resonance, was studied using high irradiation free-electron-laser soft x-ray pulses from the BL2 beamline of FLASH, DESY, Hamburg. In particular, the impact of the giant resonance on the ionisation mechanism was investigated. Ion mass-over-charge spectra were obtained by means of ion time-of-flight spectrometry. For the two photon energies, the yield of the different ionic charge states Mnq+ (q = 0���7) was determined as a function of the irradiance of the soft x-ray pulses. The maximum charge state observed was Mn6+ for resonant excitation at 52.1 eV and Mn7+ for non-resonant excitation at 61.1 eV at a maximum irradiation of 3��10 13Wcm���2. .

XXX International Conference on Photonic, Electronic, and Atomic Collisions, Cairns, Australia, 26 Jul 2017 - 1 Aug 2017 ; Journal of physics / Conference Series 875, 022044(2017). doi:10.1088/1742-6596/875/3/022044, Absolute cross sections for photoprocesses near the K edge of Ne$^{+}$ ions and neutral Ne atoms have been determined at resolving powers up to 27000 facilitating the precise determination of natural widths of the most prominent resonances as well as the associated transition probabilities and branching ratios., Published by IOP Publ., Bristol

Absolute cross sections for photoprocesses near the K edge of Ne$^{+}$ ions and neutral Ne atoms have been determined at resolving powers up to 27000 facilitating the precise determination of natural widths of the most prominent resonances as well as the associated transition probabilities and branching ratios.

Molecular crowding is ubiquitous within cells and affects many biological processes including protein-protein binding, enzyme activities and gene regulation. Here we revisit some generic effects of crowding using a combination of lattice simulations and reaction-diffusion simulations with the program ReaDDy. Specifically, we implement three reactions, simple binding, a diffusion-limited reaction and a reaction with Michaelis-Menten kinetics. Histograms of binding and unbinding times provide a detailed picture how crowding affects these reactions and how the separate effects of crowding on binding equilibrium and on diffusion act together. In addition, we discuss how crowding affects processes related to gene expression such as RNA polymerase-promoter binding and translation elongation.

Unilateral absence of a cerebellar hemisphere and vermis accompanied by contralateral malformation of the mesencephalon was diagnosed in a Hanoverian foal. The missing areas of the right cerebellar hemisphere were replaced by a cystic formation. The left part of the mesencephalic lamina quadrigemina[for full text, please go to the a.m. URL], 57th Annual Meeting of the German Society for Neuropathology and Neuroanatomy (DGNN)

Physical review letters 105(25), 253003 (2010). doi:10.1103/PhysRevLett.105.253003, Photofragmentation of the protonated water dimer $H^+(H_2O)_2$, a fundamental system both in aqueous solutions and gas-phase water clusters, has been studied at 13.8 nm using the Free Electron Laser FLASH in Hamburg. In a crossed-beam experiment using time-resolved, single-molecule fragment imaging, the two-body breakup into $H_2O^+ + H_3O^+$ was found as a prominent fragmentation channel with a kinetic energy release of up to 10 eV. This channel was observed with at least a similar yield as events with stronger fragmentation, producing protons together with neutral fragments and showing an absolute cross section of (0.5±0.2)×$10^{−18}$ $cm^2$., Published by APS, College Park, Md.

Physical review / A covering atomic, molecular, and optical physics and quantum information 98(3), 033416 (2018). doi:10.1103/PhysRevA.98.033416, In a joint experimental and theoretical endeavor, photoionization of metastable $C^{4+}$($1s\,2s\; ^3S_ 1)$ ions via intermediate levels with hollow, double-K-vacancy configurations $2s2p, 2s3p, 2p3s, 2p3d, 2s4p, 2p4s$, and $2p4d$ has been investigated. High-resolution photon-ion merged-beams measurements were carried out with the resolving power reaching up to 25 800 which is sufficient to separate the leading fine-structure components of the $2s2p^{3}P$ term. Many-body perturbation theory was employed to determine level-to-level cross sections for $K$-shell excitation with subsequent autoionization. The resonance energies were calculated with inclusion of electron correlation and radiative contributions. Their uncertainties are estimated to be below $±1$ meV. Detailed balance confirms the present photoionization cross-section results by comparison with previous dielectronic-recombination measurements. The high accuracy of the theoretical transition energies together with the present experimental results qualify photoabsorption resonances in heliumlike ions as new, greatly improved energy-reference standards at synchrotron radiation facilities., Published by APS, Woodbury, NY

Nature Communications 8(1), 2266 (2017). doi:10.1038/s41467-017-02437-9, The toolbox for imaging molecules is well-equipped today. Some techniques visualize the geometrical structure, others the electron density or electron orbitals. Molecules are many-body systems for which the correlation between the constituents is decisive and the spatial and the momentum distribution of one electron depends on those of the other electrons and the nuclei. Such correlations have escaped direct observation by imaging techniques so far. Here, we implement an imaging scheme which visualizes correlations between electrons by coincident detection of the reaction fragments after high energy photofragmentation. With this technique, we examine the H2 two-electron wave function in which electron–electron correlation beyond the mean-field level is prominent. We visualize the dependence of the wave function on the internuclear distance. High energy photoelectrons are shown to be a powerful tool for molecular imaging. Our study paves the way for future time resolved correlation imaging at FELs and laser based X-ray sources., Published by Nature Publishing Group, London

The N-methyl-D-aspartate (NMDA) type of glutamate receptor is a calcium-permeable ion channel with important functions in the physiology and pathology of the mammalian brain. NMDA receptors are critical for long-lasting, activity-induced changes in synaptic transmission, a process thought to be involved in learning and memory. NMDA receptors also control neuronal survival and cell death. How can the biological consequences of NMDA receptor activation be so diametrically opposed? The outcome of NMDA receptor activation appears to be determined by its localization. Stimulation of synaptic NMDA receptors (by synaptically-released glutamate) activates gene expression mediated by the transcription factor, cAMP-response element-binding-protein (CREB) and induces pro-survival events. In contrast, calcium flux through extrasynaptic NMDA receptors overrides these functions, shutting off CREB activity, and causing mitochondrial dysfunction and cell death. These differences in the biological response are likely due to differences in the intracellular signaling complexes associated with synaptic vs. extrasynaptic NMDA receptors. As extrasynaptic NMDA receptors are thought to be activated following hypoxic/ischemic insults, specific blockade of extrasynaptic NMDA receptors or its signaling complex may efficiently reduce neuron loss following stroke.