Mesure du coefficient de decanalisation par un defaut d'empilement dans L'or

Defects in wurtzite single crystals of ZnS, ZnSe and CdS have been observed by means of both scanning and transmission electron microscopy. Application of the scanning technique to the observation of cathodoluminescence in these materials has demonstrated localized effects on the emission close to twin boundaries and stacking faults in the as-grown crystals, which may be interpreted in terms of changes in band gap at the defect. This method has also been applied to heavy ion bombarded crystals; in addition, transmission electron microscope studies have been made of these irradiated samples and the annealing behaviour of the radiation damage has been observed. Finally, in-situ optical absorption experiments have been carried out on samples irradiated at liquid nitrogen temperature, and effects on the characteristic exciton absorption have been noted.     

Spectral narrowing and continuous tuning of a cw dye laser by grating beam-expansion

A resonator arrangement for a cw-dye laser with a holographic grating for spectral narrowing and spectral variation is described. The grating is used at the grazing incidence. With this simple design we have got linewidth smaller than 0.01 nm.     

Effects of Explosive Particle Microstructure Parameters on NQR Parameters in RDX

The effects of the particle size, density and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) content on 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) nuclear quadrupole resonance (NQR) line have been studied at 5, 10, 15 and 20?°C. The RDX line at 3.41?MHz has been measured in 17 different quality lots. The RDX line was not modified in this temperature range but was strongly altered in some lots. No significant correlation was found between line characteristics and particle sizes or particle bulk densities. Correlation coefficients were computed between the HMX content measured using high-performance liquid chromatography and the NQR line intensity and NQR line width. Significant correlations were found. They were based on the study of 11 RDX lots which exhibited 4 different HMX contents from 0 to about 9 percent in weight. Further studies are needed to precise the HMX effect in relation with the HMX location. HMX can be located inside or outside the RDX crystal. Further studies are also needed to determine the line broadening mechanism.     

Observations of vortex breakdown in an open cylindrical container with a rotating bottom

A laser induced fluorescent dye technique was used to visualize the steady-state flow driven by a rotating bottom in an open, cylindrical container. The flow behaviour and the vortex breakdown conditions were studied as a function of the container aspect ratio H/R and the Reynolds number Re = R ²/v. Like in the closed container configuration, previously studied by Vogel (1968) and Escudier (1984), vortex breakdown occurs in a certain parameter range (H/R, Re). However, in the free surface configuration vortex breakdown conditions as well as the forms of the breakdown bubbles differ notably from what is observed in the closed container configuration. In particular, it is found that as Re is increased, the breakdown bubbles get attached to the free surface and grow in diameter.     

Observation of the opto-galvanic effect in neon and argon using a nanosecond dye laser

The dynamic behavior of the opto-galvanic-effect (OGE) in Ar and Ne using a ns-dye-laser is described. The OEG signals observed by us can be subdivided into two types, which show characteristic differences in the dependence of the OEG signal on the hollow cathode lamp current.     

Nanosecond dye laser with a high-efficiency holographic grating for grazing incidence

By using a holographic grating specifically optimized for grazing incidence, it is possible to use an FP etalon in a dye laser resonator with grazing incidence. A spectral width of 4 pm with a power output of 31 kW is generated in stable operation. The influence of the mode of output coupling on the line/background ratio and the power output for grazing incidence have been investigated.     

Electron energy loss spectrometry mapping

Among electron beam microanalytical techniques, electron energy loss spectrometry (EELS) offers unique advantages in terms of information content, sensitivity, limits of detection. This paper describes new methods and tools for acquiring families of spectra over many pixels on the specimen, i.e. spectrumimages, and for processing them. Applications in different fields of research, both in materials science and in life sciences, demonstrate the potential impact of the technique for characterizing nano-sized structures.