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International audience; The study of complex reactive flows met in aeronautical engines is an experimental challenge that requires the development of noninvasive and precise measurement techniques. Coherent anti-Stokes Raman scattering (CARS) is a standard spectroscopic technique used for temperature measurements, which provides unmatched reliability and accuracy at high repetition rate thanks to its recent adaptation to femtosecond temporal regime. This paper reports the first demonstration of hybrid fs/ps-CARS thermometry in a representative aeronautical combustor (ONERA MICADO test bench, Reynolds number ≈105). Single-shot N2 CARS spectra have been recorded at 1 kHz, allowing temperature follow up, statistical and frequency (0.1–500 Hz) analysis of CH4/air flame at 0.34-MPa total pressure. The achieved results demonstrate the ability of the technique to be applied in representative engines conditions and its maturity for semi-industrial applications.

International audience; Non-invasive and accurate measurements are essential to study the reactive flows in aeronautical engines. This paper reports the results of a unique measurement campaign providing the temperature flowfield in a large scale facility turbomachine test rig using spontaneous rotational Raman scattering technique. Different planes of interest and operating conditions are probed, showing good agreement with thermocouple measurements. Fast temperature variations (>7.7 kHz) could be probed thanks to synchronization of the laser pulse with the rotor clock. Results outline the performance of in situ Raman technique to investigate steady and unsteady flows in turbine's conditions.

This paper demonstrates a new arrangement for wide-field CARS imaging. The setup using nanosecond dye lasers in a non-phase-matching illumination is presented. The chemical selectivity of the signal is demonstrated on polystyrene beads. Moreover, the experimental arrangement has enabled the acquisition of images of living cells in suspension with a satisfactory signal-to-background ratio by using only a single pair of laser shots. Therefore, each image can be acquired using a total duration of 3 ns, which is the pulse duration of the laser used in this study. Finally, lack of damage on cells has been demonstrated in conditions leading to strong CARS signal generation. In particular, no cell morphological changes were observed and cell membrane integrity (assessed by trypan blue test) was preserved. Copyright © 2012 John Wiley & Sons, Ltd.

The optoelectronic properties of hexagonal boron-nitride and boron-nitride nanotubes (BNNTs) are investigated by using photoconductivity experiments, associated to photoluminescence excitation analysis. By this way, excitations related to the conduction band of hexagonal boron-nitride have been experimentally determined, as well as the free excitonic level. Multiwalled boron-nitride nanotubes have also been lead by using these methods and the first results suggest some hypotheses about the band gap energy and the nature of the various absorptions, which occur under an UV excitation. These experimental results are presented and discussed and some perspectives are finally suggested.

The main consequence of the interaction between cells and pulsed electric fields is the destabilization of the plasma membrane leading to its permeabilization. Previous vibrational spectroscopy studies (S.M. Gruenbaum et al., J. Chem. Phys., 135, 2011) have shown that interfacial water is highly organized around the phospholipids of the membrane. Moreover, various numerical studies (such as Molecular Dynamics simulations) have shown that the interfacial water is highly disturbed by the pulsed electric field. We detail here a study of the behavior of the interfacial water around biological objects, before and after exposition to intense pulsed electric fields, by Coherent Anti-stokes Raman Scattering (CARS) spectroscopy.

Individual multiwall boron nitride nanotubes with diameters from 30 nm to 110 nm are shown to be efficient UV emitters by cathodoluminescence. Their luminescence does not evolve much in this diameter range, with dominant UV recombinations at about 230 nm. As a result, single nanotube properties can be obtained from experiments performed on ensembles of nanotubes. Such ensembles are studied by photoluminescence as a function of temperature 5 K‐300 K and by photoluminescence excitation experiments at 9 K. The results are discussed and compared with the related bulk material, hexagonal boron nitride. The strong luminescence recorded around 230 nm is attributed to excitonic effects, more precisely to excitons bound to the structural defects: dislocations, facets, which are observed along the walls.

Cathodoluminescence imaging and spectroscopy experiments on a single bamboo-like boron nitride nanotube are reported. Imaging experiments show that the luminescence is located all along the nanotube. Spectroscopy experiments point out the important role of dimensionality in this one dimensional object.

M. G. Silly,1,2 P. Jaffrennou,1,2,4 J. Barjon,3 J.-S. Lauret,4 F. Ducastelle,1,* A. Loiseau,1 E. Obraztsova,5 B. Attal-Tretout,2 and E. Rosencher2 1Laboratoire d’Etude des Microstructures, ONERA-CNRS, Boite Postale 72, 92322 Châtillon Cedex, France 2Departement de Mesures Physiques, ONERA, Chemin de la Huniere, 91761 Palaiseau Cedex, France 3Groupe d’Etude de la Matiere Condensee, Universite de Versailles St. Quentin, CNRS Bellevue, 1 place Aristide Briand, 92195 Meudon Cedex, France 4Laboratoire de Photonique Quantique et Moleculaire, Institut d’Alembert, Ecole Normale Superieure de Cachan, 61 Avenue du President Wilson, 94235 Cachan Cedex, France 5A. M. Prokhorov General Physics Institute of Russian Academy of Sciences, 38 Vavilov Street, 119991 Moscow, Russia Received 27 July 2006; revised manuscript received 21 December 2006; published 12 February 2007

The excitonic recombinations in hexagonal boron nitride (hBN) are investigated with spatially resolved cathodoluminescence spectroscopy in the UV range. Cathodoluminescence images of an individual hBN crystallite reveals that the 215 nm free excitonic line is quite homogeneously emitted along the crystallite whereas the 220 nm and 227 nm excitonic emissions are located in specific regions of the crystallite. Transmission electron microscopy images show that these regions contain a high density of crystalline defects. This suggests that both the 220 nm and 227 nm emissions are produced by the recombination of excitons bound to structural defects.

In this paper, we report about an application of the two-color laser-induced thermal gratings technique in the visible region to the detection of nitrogen dioxide in mixtures of nitrogen and argon at total pressure ranging up to 1 bar. We have investigated the dependence of the signal on the gas mixture parameters (pressure, NO 2 concentration, collision partners) and on the laser properties (beams polarization, pulse energy, bandwidth) at various instants during the temporal evolution of the thermal grating. Comparison of experimental results and theoretical predictions is performed. Finally, the detectivity of 4 ppm was obtained at normal conditions of pressure (1 bar) and temperature (300 K).

International audience; Laser-induced fluorescence (LIF) measurements of OH were performed in flat stoichiometric CH4/air flames burning at 1, 3, 5, 7, and 9.6 bar, which had previously been investigated using OH resonance CARS. In the LIF study, line shape information and temperatures were extracted from excitation spectra; in addition, OH profiles as a function of height above the burner surface and an estimate of the OH concentration for the different flames were obtained. The perspectives and feasibility of quantitative fluorescence measurements in high pressure flames are discussed, particularly in comparison with the application of resonance CARS.