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Brenier A.,CNRS Laboratory of Physical Chemistry of Luminescent Materials
Laser Physics Letters | Year: 2011

We have demonstrated a simple and compact tunable dual-wavelength Yb 3+:KGd(WO 4) 2 (Yb:KGW) laser. The laser is diode pumped through an optical bifurcated fiber and an adjustable beamsplitter. Thanks to two transversally chirped volume Bragg gratings (TCVBG) used as output couplers, the frequency difference between the two collinear waves is continuously tunable from 0 up to 7.8 THz with 110 GHz bandwidth. The frequency range is only limited by non optimized optical components and not by the principle of functioning. © 2011 by Astro Ltd., published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA.

Brenier A.,CNRS Laboratory of Physical Chemistry of Luminescent Materials | Wu Y.,CAS Institute of Chemistry | Zhang J.,CAS Institute of Chemistry | Wu Y.,University of Chinese Academy of Sciences
Applied Physics B: Lasers and Optics | Year: 2012

We report spectroscopic and laser properties for propagation directions outside the principal axes of Yb 3+-doped low symmetry laser crystals with a special devotion to the wavelength dependence anisotropy. We illustrate our report with experimental data in the 900-1075 nm range of wavelengths from the Yb 3+:La 2CaB 10O 19 monoclinic crystal excited under laser diode pumping at 975 nm. This study, which makes easier the realization of Yb 3+ lasers with an efficient free-running operation at the wavelength having the highest emission intensity or at a specified wavelength, or emitting two frequencies with a specified frequency difference, is of promising interest for applications. © 2011 Springer-Verlag.

Shoval S.,Open University of Israel | Yadin E.,Tel Aviv University | Panczer G.,CNRS Laboratory of Physical Chemistry of Luminescent Materials
Journal of Thermal Analysis and Calorimetry | Year: 2011

The work deals with the FT-IR and micro- Raman spectroscopy study of the pseudo-amorphous and crystalline thermal phases in the composition of calcareous Iron Age pottery from the Galilee. The application of second-derivative and curve-fitting techniques improves the identification of the thermal phases in the composition of the pottery and makes it possible to analyze the pseudoamorphous phases which are formed during the firing of the clayey raw material to pottery. This technique makes it possible to distinguish between meta-smectite and metakaolinite and to estimate the firing temperature of the pottery. The Micro-Raman spectroscopy is sensitive to the structural degree of ordering of the thermal phases and enables point analysis of peculiar components in the composition of the pottery. Based on the spectroscopic study, it is concluded that the calcareous pottery contained large amounts of microcrystalline-recarbonated calcite mixed with the meta-clay. The large amount of recarbonated calcite in the pottery material and the relatively low firing temperature indicates that instead of sintering the clay, lime technology was used for the cementation of the calcareous vessels. This process took place after the firing by recarbonation of the decomposed calcite which leads to cementation of the vessels with microcrystalline calcite. © 2011 Akadémiai Kiadó, Budapest, Hungary.

Garbarino S.,INRS E nergie | Pereira A.,CNRS Laboratory of Physical Chemistry of Luminescent Materials | Hamel C.,INRS E nergie | Irissou E.,INRS E nergie | And 2 more authors.
Journal of Physical Chemistry C | Year: 2010

Pulsed laser deposition was used to prepare Pt nanoparticles of various sizes ranging from 1.8 to 6.0 nm.These nanoparticles were deposited on highly oriented pyrolytic graphite (HOPG) and gold substrates. For Pt deposited on HOPG and Au, the size of the nanoparticles was established by scanning tunneling microscopy (STM) and calculated from the electrochemically active surface area (EASA) obtained through measurements of the hydrogen underpotential deposited charges, QHupd. The diameters determined from these two sets of measurements agreed with each other to within 60%. X-ray photoelectron spectroscopy (XPS) was used to assess the size of the nanoparticles before and after an electrochemical treatment that involved potential cycling in 0.5 M H2SO4. The upper potential limit was progressively increased from 1.15 to 1.40 V in steps of 0.05 V, and the EASA was continuously monitored. The EASA decreased with cycle number and with increasing upper potential limit to 1.35 V vs RHE. This effect was found to be larger for the smaller Pt nanoparticles (50% decrease for φ ) 1.8 nm) than for the larger ones (20% decrease for φ ) 3.0 nm). It was found by XPS that the diameter of the smaller Pt nanoparticles increased from φ ) 1.8 nm to φ ) 6.5 nm as a result of the electrochemical treatment, whereas the diameter of the larger nanoparticles (φ ) 3.0 nm) remained constant. In this potential range, the corrosion of the gold substrate is minimal, and this observation can be explained by an increase of the equilibrium soluble Pt concentration with decreasing Pt nanoparticle diameter. © 2010 American Chemical Society.

Jierry L.,Charles Sadron Institute | Harthong S.,Ecole Normale Superieure de Lyon | Aronica C.,Ecole Normale Superieure de Lyon | Mulatier J.-C.,Ecole Normale Superieure de Lyon | And 2 more authors.
Organic Letters | Year: 2012

Herein, we describe our recent expeditious synthesis of dibenzo[c]acridine helicene-like compounds on a large scale in pure enantiomeric form. This flexible synthesis allows for variation at several positions on the skeleton. Geometrical parameters related to these compounds have been obtained from monocrystal X-ray structure resolution. Additionally, chiroptical parameters have been recorded, highlighting the versatility of this family showing for example optical rotation at 589 nm varying between 135 and 150 deg g -1cm 2. © 2011 American Chemical Society.

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