Ch. Streli

Laser technology: source of coherent kiloelectronvolt X-rays.

Generating X-rays that have the properties of laser light has been a long-standing goal for experimental science. Here we describe the emission of highly collimated, spatially coherent X-rays, at a wavelength of about 1 nanometre and at photon energies extending to 1.3 kiloelectronvolts, from atoms that have been ionized by a 5-femtosecond laser pulse. This means that a laboratory source of laser-like, kiloelectronvolt X-rays, which will operate on timescales relevant to many chemical, biological and materials problems, is now within reach.

Analysis of Ni on Si-wafer surfaces using synchrotron radiation excited total reflection X-ray fluorescence analysis

Abstract Total Reflection X-Ray Fluorescence Analysis excited with synchrotron radiation (SR-TXRF) monochromatized by a multilayer (ML) has been used for the analysis of Ni on Si-wafer surfaces. Intentionally contaminated wafers using droplet samples have been used to determine the detection limits. Two different kinds of the geometrical arrangement of sample and detector have been compared, one of them resulting in detection limits of 13 fg for Ni. Experiments have been performed at Hasylab, Beam L using a bending magnet radiation.

Total Reflection X‐Ray Fluorescence Analysis Excited by Synchrotron Radiation (SR‐TXRF): Variation of Excitation Conditions and Sample Geometries

The use of synchrotron radiation as the excitation source for total reflection x-ray fluorescence analysis (SR-TXRF) in combination with a multilayer structure for monochromatization led to detection limits in the femtogram range for medium-Z elements. Experiments were performed at the Hasylab Beamline L using bending magnet radiation. Different methods for the modification of the spectral distribution, viz. multilayer monochromatization, insertion of a high-energy cut-off and a simple filter technique, were compared. Also, several possible types of geometrical arrangement of the sample and detector were examined to establish whether an improvement in excitation or detection conditions is possible. Samples were of evaporated droplets of aqueous or acidic solutions of several elements at various concentrations. Spectra were evaluated and the data used to extrapolate the detection limits (DL). Monochromatization of the synchrotron radiation in combination with a sample carrier positioned in the vertical plane and a side-looking detector in the plane of polarization turned out to give the best results with a DL of 15 fg for Ni.

Generation of coherent keV x-rays with intense femtosecond laser pulses

The realization of a compact laboratory x-ray source delivering spatially and temporally coherent ultrashort pulses is of great interest for time-resolved x-ray spectroscopy. Here, we describe the design and the parameters of a short wavelength source based on high-harmonic generation (HHG) delivering radiation up to 1.3 keV. The extension of the cutoff is attributed to intense few-cycle driving laser pulses delivered via a tabletop near-infrared laser system.

Direct total-reflection X-ray fluorescence trace element analysis of organic matrix materials with a semiempirical standard

Abstract In this work we describe a method for trace element analysis in organic matrix materials using direct irradiation of the sample in a total-reflection X-ray fluorescence spectrometer. The method avoids: (i) the need to digest the organic material, (ii) the need to add an internal standard to the unknown specimens, and (iii) the need to weigh the test specimen. Quantification of unknowns is achieved with the scattered peak as the internal standard and a semiempirical computational model of a standard, instead of a real reference material, for spectrometer sensitivity calibration. Spectra of certified standard reference materials with an organic matrix, obtained with a monochromatized beam from an X-ray tube, were quantified, showing good agreement with nominal, certified or previously reported values for solid and liquid samples.

Quasi-Phase-Matched High-Order Harmonic Generation in the Soft-X-ray Regime

We realized quasi-phase-matched generation of soft x-rays emitted from two gas jets. The harmonic signal has been enhanced in a broad range (from 250 eV to 600 eV) and up to two orders of magnitude around 400 eV

Coherent kiloelectronvolt X-ray emission from laser-driven atoms

J. Seres1, E. Seres1,2, Ch. Streli3, P. Wobrauschek3, Ch. Spielmann2, F. Krausz1,4,5 1Institut für Photonik, Technische Universität Wien, Austria; 2 Physikalisches Institut EP1, Universität Würzburg, Germany; 3Atominstitut der Österreichischen Universtitäten, Technische Universität Wien, Austria; 4Max-Planck-Institut für Quantenoptik, Germany; 5Department für Physik, Ludwig-Maximilians-Universität München, Germany jozsef.seres@tuwien.ac.at,

Femtosecond X-ray fluorescence from light elements excited by laser harmonics

Summary form only given. We report the observation of K-shell vacancies in light elements, such as boron and carbon, by means of X-ray fluorescence using sub-10-fs-pulse-driven coherent laser harmonics as the excitation source. The experiments represent the first application of coherent water-window radiation produced by a laboratory source and are a first step towards time-resolved X-ray spectroscopy of solid-state and molecular dynamics on a sub-100-fs time scale.