A non-destructive view with X-rays into the strain state of bronze axes.

In this paper we present a new approach using highly surface sensitive X-ray diffraction methods for archaeometrical investigation highlighted on the Neolithic Axe of Ahneby. Applying the sin2Ψ-method with a scintillation detector and a MAXIM camera setup, both usually applied for material strain analysis on modern metal fabrics. We can distinguish between different production states of bronze axes: Cast, forged and tempered. The method can be applied as a local probe of some 100th of μm2 or integrative on a square centimeter surface area. We applied established synchrotron radiation based methods of material strain mapping and diffraction on a Neolithic bronze axe as well as replicated material for noninvasive analysis. The main goal of the described investigations was to identify the effects upon the bronze objects of post cast surface treatment with stone tools and of heat treatment

Concentration effects on the dynamics of liquid crystalline self-assembly: Time-resolved X-ray scattering studies.

A manifold of ordering transitions relevant to chemical and biological systems occur at interfaces from liquids to self-assembled soft solids like membranes or liquid crystals. In the present case, we were interested in understanding the phase transition from the microemulsion phase to the liquid crystal phase in terms of their driving forces, i.e., activation energy and entropy. The purpose of this work was to clarify the influence of concentration effects of the amphiphilic molecules on the nature of these self-assembly processes. By photosensitization of the model system (polyalkylglycolether (C(10)E(4)), water, decane, and cyclohexane) with laser dyes, we could effectively induce and control the phase transition through the absorption of optical photons. The photo transformation conditions were chosen in such a way that the system was in thermal equilibrium. By application of time-resolved photo small-angle X-ray scattering we could monitor the conversion process and demonstrate that the surfactant concentration has a direct impact on the activation energy, which is observable through the length of the induction time

Investigation of the ultra-fast structural changes in metal-organic complexes: comparison spectroscopy and time-resolved XRD

Our aim is a detailed understanding of the ultrafast structrual dynamics and the underlying basic machanisms of molecular switches under optical excitation, which are still not fully understood in its variety. In order to monitor the occurring structural changes in molecules and alloys we are taking advantage of time-resolved x-ray diffraction measurements. but since the important electronic changes due to optical excitation take place on very short ps- and sub-ps timescales it gives rise to the necessity of faster time resolved measurements than those which are currently possible at third generation synchrotrons. Besides new attempts of directly monitoring the structural changes with shorter x-ray pulses by femtosecond FEL- an XPS-pump-probe experiments, we are currently gaining more insight in the structural dynamics by indirect measurements using our fs-time-resolved transient absorption spectroscopy. Therefore we will present our recent spectroscopic data of a metal-organic complex which will be related to certain structural changes, while the near future aim is to prove these by further x-ray experiments

Homoleptic tetraazaphenanthrene-based copper(I) complexes:Synthesis, spectroscopic characterization, crystal structures and computational studies

Three new Cu(I) complexes containing bidentate N^N donor ligands with the general formula [Cu(N^N)2][PF6] (N^N = 2,3-diphenyl-6,7-di-p-tolyl-1,4,5,8-tetraazaphenanthrene (L1), 2,3-diphenyl-6,7-di(2-thienyl)-1,4,5,8-tetraazaphenanthrene (L2), and 2,3-diphenyl-6,7-di-p-fluorophenyl-1,4,5,8-tetraazaphenanthrene (L3), were prepared by the reaction of [Cu(CH3CN)4][PF6] with two equivalents of the N^N ligand. Single-crystal X-ray diffraction analysis confirmed that in each complex the metal displays a distorted tetrahedral geometry surrounded by the four N atoms of the two sterically hindered substituted tetraazaphenanthrene (TAP) ligands. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT), calculations were used to study the ground state properties and interpret the absorption spectra for these Cu(I) complexes. The calculations show that the lowest-energy excitations of all complexes are dominated by dπ(Cu) → π∗(L), metal-to-ligand charge transfer, (MLCT) excitations. Electronic difference density maps (EDDMs) were calculated, indicating the change of electron density in the singlet excited states. The degree of filling of the coordination sphere (G parameter) by the ligands was calculated taking into account the ligand–ligand overlap, and compared to the related bis(2,9-disubstituted phenanthroline) Cu(I) complexes

A new compact soft x ray spectrometer for resonant inelastic x ray scattering studies at PETRA III

We present a newly designed compact grating spectrometer for the energy range from 210 eV to 1250 eV, which would include the K amp; 945;1,2 emission lines of vital elements like C, N, and O. The spectrometer is based on a grazing incidence spherical varied line spacing grating with 2400 l mm at its center and a radius of curvature of 58 542 mm. First, results show a resolving power of around 1000 at an energy of 550 eV and a working spectrometer for high vacuum 10 amp; 8722;4 mbar environment without losing photon intensit

Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17