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Single and double photoionization of the Li-like B ion: Strong ionization-excitation contributions
No full textSingle and double photoionization of the Li-like B (1s2sS) ion were studied both experimentally and theoretically in the energy range from approximately 250–1200 eV. The cross section for net single ionization in that range is dominated by direct removal of one K-shell electron, a process that is described very well by theory. Accordingly, measured yields of B photoproducts were normalized to theory to obtain absolute cross sections . Aside from direct single ionization, there are additional contributions to from photoabsorption resonances. The parameters of the Fano profile of the most prominent of these resonances, the triply excited 22pSP state, were calculated by employing the convergent close coupling (CCC) approach and the theoretical results were experimentally verified. Using the normalization procedure obtained from the investigation of single ionization, also the measured yields of B product ions could be put on an absolute cross-section scale. The resulting experimental cross section is in good accord with the CCC calculations revealing unexpectedly strong contributions that arise from ionization with excitation of B (1s2sS) forming intermediate autoionizing B (nln'l') levels, which subsequently decay to B by Auger-electron emission. In addition, contributions to from resonant excitation of B (nln'l'n''l'') with n, n', n'' >= 2 could be identified. These triply excited resonances with an empty K shell can decay by simultaneous or sequential emission of two electrons and thus contribute to net double photoionization of the parent B ion
Ductilization of 2.6-GPa alloys via short-range ordered interfaces and supranano precipitates
No full textHigher strength and higher ductility are desirable for structural materials. However, ultrastrong alloys inevitably show decreased strain-hardening capacity, limiting their uniform elongation. We present a supranano (<10 nanometers) and short-range ordering design for grain interiors and grain boundary regions, respectively, in fine-grained alloys based on vanadium, cobalt, and nickel, with additions of tungsten, copper, aluminum, and boron. The pronounced grain boundary–related strengthening and ductilization mechanism is realized through segregation of the short-range ordering near the grain boundary. Furthermore, the supranano ordering with a larger size has an enhanced pinning effect for dislocations and stacking faults, multiplied and accumulated in grain interiors during plastic deformation. These mechanisms promote continuously increased flow stress until fracture of the alloy at 10% strain with 2.6-gigapascal tensile stress
Structural insights of mechanochemically amorphised MIL-125-NH
No full textIn this work, we investigated the response of the metal–organic framework MIL-125-NH to ball-milling. Both localised and bulk analyses revealed prolongued ball-milling results in a complete loss of long-range structural order. Investigation of this disorder revealed partial retention of the local bonding of the secondary building unit, suggesting structure collapse progressed primarily through metal–linker bond breakage. We explored the photocatalytic performance of the materials, and examined the materials’ band gap using UV-Vis reflectance spectroscopy
Investigation on the formation of two dimensional perovskite nanostructures at the water surface through self initiated reaction
No full textThe emerging class of hybrid organic-inorganic perovskites (HOIPs) has exhibited fascinating properties for a wide range of technological applications. With halide ions, HOIPs have provided novel optoelectronic devices including efficient solar cells and with pseudohalide anions-like formate (HCOO), enigmatic electromagnetic properties have been obtained in HOIPs. Large-scale synthesis of such 2D HOIP films is of immense importance for the advancement of its application as solar materials. We have shown using in-situ X-ray measurements that the Langmuir monolayer of perovskite can be formed at the air-water interface by spreading stearic acid molecules on the water subphase having (CHNH)PbBr molecules. The 2D lead formate perovskite films are formed at the air-water interface through a self-initiated reaction and the in-situ X-ray scattering and ex-situ Raman spectroscopy measurements revealed this reaction process. The spreading of lipid molecules having positive and negative head-group charges as surfactants over the water surface shows that the formation of perovskite nanofilms at the air-water interface specifically requires the presence of HCOO head-group of stearic acid. In this room temperature interfacial reaction, formate anions come from the stearic acid monolayer present on the water surface and completely replace bromines in the perovskite present in water subphase to form (BA)Pb(HCOO) at the air-water interface. Our results show an easy route for large-scale synthesis of 2D pseudohalide perovskites
Quinizarin Gold(I) N‐Heterocyclic Carbene Complexes with Synergistic Activity Against Anthracycline‐Resistant Leukaemia Cells: Synthesis and Biological Activity Studies
No full textNew, asymmetric quinizarin-Au(I)-NHC complexes were designed, isolated, and fully characterised including by single crystal X-ray crystallography. Cytotoxicity studies showed effective growth inhibition in HeLa cervical cancer cells with IC values ranging from 2.4 μM to 5.3 μM. The successful cellular uptake was evidenced by X-ray fluorescence imaging on cryo-preserved whole HeLa cells and the sub-cellular localisation was monitored by live-cell fluorescence microscopy. Notably, complex 2 b showed circumvention of acquired anthracycline resistance in K562 leukaemia cells as well as synergistic activity with doxorubicin against both wild-type and anthracycline-resistant Nalm-6 leukaemia cells. Interestingly, sub-cellular localisation towards mitochondria proved to be more important than the compounds’ overall cytotoxicity for potent antiproliferative activity and to achieve effective resistance circumvention
Search for -channel scalar and vector leptoquark exchange in the high-mass dimuon and dielectron spectra in proton-proton collisions at = 13 TeV
No full textA search for -channel exchange of leptoquarks (LQs) is performed in dimuon and dielectron spectra using proton-proton collision data collected at = 13 TeV with the CMS detector at the CERN LHC. The data correspond to an integrated luminosity of 138 fb. Eight scenarios are considered, in which scalar or vector LQs couple up or down quarks to muons or electrons, for dilepton invariant masses above 500 GeV. The LQ masses are probed up to 5 TeV, beyond a regime probed by previous pair-production and single-production searches. The differential distributions of dilepton events are fit to templates that model the nonresonant LQ exchange and various standard model background processes. Limits are set on LQ-fermion coupling strengths for scalar and vector LQ masses in the 1-5 TeV range at 95% confidence level, establishing stringent limits on first- and second-generation LQs
Evidence of medium response to hard probes using correlations of Z bosons with hadrons in heavy ion collisions
No full textThe first measurement of pseudorapidity and azimuthal angle distributions relative to the momentum vector of a Z boson for low transverse momentum () charged hadrons in lead-lead (PbPb) collisions is presented. By studying the hadrons produced in an event with a high- Z boson (40 350 GeV), the analysis probes how the quark-gluon plasma (QGP) medium created in these collisions affects the parton recoiling opposite to the Z boson. Utilizing PbPb data at a nucleon-nucleon center-of-mass energy = 5.02 TeV from 2018 with an integrated luminosity of 1.67 nb and proton-proton (pp) data at the same energy from 2017 with 301 pb, the distributions are examined in bins of charged-hadron . A significant modification of the distributions for charged hadrons in the range 1 2 GeV in PbPb collisions is observed when compared to reference measurements from pp collisions. The data provide new information about the correlation between hard and soft particles in heavy ion collisions, which can be used to test predictions of various jet quenching models. The results are consistent with expectations of a hydrodynamic wake created when the QGP is depleted of energy by the parton propagating through it. Based on comparisons of PbPb data with pp references and predictions from theoretical models, this Letter presents the first evidence of medium-recoil and medium-hole effects caused by a hard probe
Spatially Resolved In Situ X-ray Absorption Spectroscopy Studies of ZnS Nanoparticle Synthesis at the Water–Toluene Interface
No full textTwo-phase synthesis is a well-established approach for achieving precise control of the nanoparticle properties. However, studying and understanding chemical transformations in such a spatially heterogeneous system is challenging. In this work, we introduce a two-phase synthesis route for ZnS nanoparticles (ZnS NPs) at the water–toluene interface. By employing spatially resolved in situ high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS) combined with density functional theory (DFT) calculations, we track the diffusion of Zn species at the interface, identify key reaction intermediates, and monitor the nucleation and growth of ZnS NPs within the toluene phase. We propose the formation of a [Zn(HO)] complex upon dissolving Zn(Ac) in water and the diffusion of Zn ions from water to toluene driven by the formation of an octahedral [Zn(OA)] complex (OA = oleylamine). Furthermore, by complementing HERFD-XAS with total X-ray scattering analysis, we show the formation of an intermediate tetrahedral [Zn(SR)4] complex at 60 °C and its successive transformation to noncrystalline ZnS nuclei at 80 °C and crystalline ZnS NPs starting at 100 °C. Thus, we demonstrate how in situ X-ray spectroscopy can elucidate the coordination and diffusion of Zn ions, and, in combination with X-ray scattering studies, identify the emergence of atomic and electronic structures during the two-phase synthesis of ZnS nanoparticles
Rocking scans of Pd/AlO under CH oxidation conditions - Cycle I
No full textMovies of the HEGIXRD rocking scans of Pd/AlO catalyst for full CH oxidation under operation during the first experiment cycle. The scans are recorded at 523K, 573K, 623K, 673K, and 723K with a reactor pressure of 100mbar, a total flow 100ml/min and a composition of 20% O, 0.1% CH, and 79.9% Ar