Recent developments in X-UV optics and X-UV diagnostics

Metrology of XUV beams (X-ray lasers, high-harmonic generation and VUV free-electron lasers) is of crucial importance for the development of applications. We have thus developed several new optical systems enabling us to measure the optical properties of XUV beams. By use of a Michelson interferometer working as a Fourier-transform spectrometer, the line shapes of different X-ray lasers have been measured with a very high accuracy (/10^-6). Achievement of the first XUV wavefront sensor has enabled us to measure the beam quality of laser-pumped as well as discharge-pumped X-ray lasers. A capillary discharge X-ray laser has demonstrated a very good wavefront allowing us to achieve an intensity as high as 3×10¹⁴ Wcm^-2 by focusing with a f=5 cm mirror. The sensor accuracy has been measured using a calibrated spherical wave generated by diffraction. The accuracy has been estimated to be as good as /120 at 13 nm. Commercial developments are underway. At Laboratoire dOptique Appliquée, we are setting up a new beamline based on high-harmonic generation in order to start the femtosecond, coherent XUV optic . PACS 07.85.Nc;32.70.Jz;41.50.+h;42.15.Dp;42.55.Vc;52.70.La     

Optimization of the focused flux of high harmonics

Following the theoretical predictions [1], the observation of two-photon processes by interaction of vacuum ultraviolet (VUV) radiation with inner-shell levels of atoms requires focused intensities in the 10¹³-10¹⁴ W/cm² range. Our aim is to reach this regime in order to study non-linear optics at these wavelengths. We first optimized the high harmonic conversion efficiency in argon by studying the best experimental conditions for phase-matching, concentrating on focus geometry related to laser energy, cell length and position relative to the focus. We then studied the resulting harmonic beam focusability by a toroidal mirror (f=10 cm) and made an image of the harmonic focus. We conclude with an evaluation of the focused intensity that we are able to reach experimentally.Received: 28 January 2003, Published online: 24 April 2003PACS: 32.80.Rm Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) - 42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation     

Hartmann wave-front measurement at 13.4 nm with lambdaEUV/120 accuracy

We report, for the first time to our knowledge, experimental demonstration of wave-front analysis via the Hartmann technique in the extreme ultraviolet range. The reference wave front needed to calibrate the sensor was generated by spatially filtering a focused undulator beam with 1.7- and 0.6-microm-diameter pinholes. To fully characterize the sensor, accuracy and sensitivity measurements were performed. The incident beam's wavelength was varied from 7 to 25 nm. Measurements of accuracy better than lambdaEUV/120 (0.11 nm) were obtained at lambdaEUV = 13.4 nm. The aberrations introduced by an additional thin mirror, as well as wave front of the spatially unfiltered incident beam, were also measured.     

The mechanism of magnetic interactions in the bulk ferromagnet para-(methylthio)phenyl nitronyl nitroxide (YUJNEW): a first principles, bottom-up, theoretical study

The mechanism of magnetic interactions in the bulk ferromagnet para-(methylthio)phenyl nitronyl nitroxide crystal (YUJNEW) has been theoretically reinvestigated, using only data from ab initio calculations and avoiding any a priori assumptions. We first calculate the microscopic magnetic interactions (JAB exchange couplings) between all unique radical pairs in the crystal, and then generate the macroscopic magnetic properties from the energy levels of the corresponding Heisenberg Hamiltonian. We thus propose a first principles, bottom-up (i.e. micro-to-macro) approach that brings theory and experiment together. We have applied this strategy to study the magnetism of YUJNEW using data from the previously reported 298 and 114 K crystal structures, and also data from a 10 K neutron diffraction structure fully reported in this work. The magnetic topology at 298 K is two-dimensional: noninteracting planes, with three different in-plane JAB pair interactions (+0.24, +0.09, and -0.11 cm(-1)) and one numerically negligible (+0.02 cm(-1)) inter-plane JAB interaction. In contrast, the magnetic topology at 114 and 10 K is three-dimensional, with two non-negligible in-plane JAB constants (+0.11 and +0.07 cm(-1) at 114 K; +0.22 and +0.07 cm(-1) at 10 K) and one inter-plane pair interaction (+0.07 cm(-1) at 114 K; +0.08 cm(-1) at 10 K). Although this three-dimensional magnetic topology is consistent with YUJNEW being a bulk ferromagnet, there is only a qualitative agreement between computed and experimental magnetic susceptibility chiT(T) data at 114 K. However, the experimental chiT(T) curve is quantitatively reproduced at 10 K. The heat capacity curve presents a peak at around 0.12 K, close to the estimated experimental peak (0.20 K).     

Unprecedented highly stereoselective alpha- and beta-C-glycosidation with chiral titanium enolates

[reaction: see text] Lewis acid mediated addition of chiral titanium enolates to glycals provides either alpha- or beta-1'-methyl-substituted C-glycosides. This highly stereoselective methodology permits the modular preparation of three of the four possible diastereomers.     

Characterization of the automorphism group of quaternary linear Hadamard codes

A quaternary linear Hadamard code ${\mathcal{C}}$ is a code over ${\mathbb{Z}_4}$ such that, under the Gray map, gives a binary Hadamard code. The permutation automorphism group of a quaternary linear code ${\mathcal{C}}$ of length n is defined as ${{\rm PAut}(\mathcal{C}) = \{\sigma \in S_{n} : \sigma(\mathcal{C}) = \mathcal{C}\}}$ . In this paper, the order of the permutation automorphism group of a family of quaternary linear Hadamard codes is established. Moreover, these groups are completely characterized by computing the orbits of the action of ${{\rm PAut}(\mathcal{C})}$ on ${\mathcal{C}}$ and by giving the generators of the group. Since the dual of a Hadamard code is an extended 1-perfect code in the quaternary sense, the permutation automorphism group of these codes is also computed.     

Quadriwave lateral shearing interferometry in an achromatic and continuously self-imaging regime for future x-ray phase imaging

We present in this Letter a type of quadriwave lateral shearing interferometer for x-ray phase imaging. This device is based on a phase chessboard, and we take advantage of the large spectrum of the source to produce interferograms with a propagation-invariant contrast. Such a grating has been created for hard x-ray interferometry and experimentally tested on a synchrotron beamline at Soleil.     

Nucleophilic aryl fluorination and aryl halide exchange mediated by a Cu(I)/Cu(III) catalytic cycle

Copper-catalyzed halide exchange reactions under very mild reaction conditions are described for the first time using a family of model aryl halide substrates. All combinations of halide exchange (I, Br, Cl, F) are observed using catalytic amounts of Cu(I). Strikingly, quantitative fluorination of aryl-X substrates is also achieved catalytically at room temperature, using common F(-) sources, via the intermediacy of aryl-Cu(III)-X species. Experimental and computational data support a redox Cu(I)/Cu(III) catalytic cycle involving aryl-X oxidative addition at the Cu(I) center, followed by halide exchange and reductive elimination steps. Additionally, defluorination of the aryl-F model system can be also achieved with Cu(I) at room temperature operating under a Cu(I)/Cu(III) redox pair.     

Dimerization of Pyramidalized 3,4,8,9‐Tetramethyltetracyclo [4.4.0.03,9.04,8]dec‐1(6)‐ene to a Hydrocarbon Featuring Four Cyclohexane Rings in Boat Conformations

The synthesis, chemical trapping, and dimerization of a highly pyramidalized alkene is reported. Its dimer is a unique nonacycle featuring three planar cyclobutane rings, four cyclopentane rings, and four cyclohexane rings in boat conformations. The X‐ray diffraction analysis showed a H–H distance between the flagpole hydrogen atoms of 1.999 Å and a separation of 2.619 Å between the two flagpole carbon atoms. The three cyclobutane rings of the dimer were thermally stable.     

Robust hierarchical production planning under uncertainty

We consider aggregation of products with similar characteristics in a two-level hierarchical production planning model. A robust aggregate plan at the upper level is such that, at the lower level, a disaggregation policy exists even when detailed demands may vary within some given bounds. We provide necessary and sufficient conditions for the robustness of an aggregate plan and obtain a closed form expression of these conditions. A set of more manageable sufficient conditions is also presented.Institut National des Sciences Appliquées de Toulouse.