SPECTROSCOPIE LASER DE LENTILLE THERMIQUE : INFLUENCE DES PROPRIÉTÉS PHOTOTHERMIQUES DU SOLVANT

La spectroscopie de lentille thermique (thermal lensing) est une technique de plus en plus utilisée en Chimie Analytique pour améliorer les limites de détection des échantillons faiblement absorbants et non fluorescents. Le principe de la méthode repose sur la création, dans l'échantillon, d'une lentille thermique, consécutivement à l'échauffement produit par la relaxation non radiative des molécules excitées par un faisceau laser incident. Le phénomène d'absorption est suivi en mesurant, à l'aide d'un détecteur placé en champ lointain, la variation d'intensité au centre du faisceau

Étude de transferts d'excitation dans un plasma induit par haute fréquence entre gaz plasmagène et éléments introduits

Studies of injected elements in an inductively coupled argon plasma working at atmospheric pressure show a departure from L. T. E. This is confirmed by the discrepancies between the ionization temperature and the excitation temperatures. The excitation of some lines of these elements can be explained through the action of metastable levels of neutral and ionized argon. An atomic absorption experiment using a two-line method has been set up in order to measure the metastable densities.L'étude de l'excitation des éléments injectés dans un plasma d'argon induit par haute fréquence à la pression atmosphérique montre que l'hypothèse de l'E. T. L. n'est pas vérifiée. Ce fait est confirmé par la différence obtenue entre la température d'ionisation et celles d'excitation. L'excitation de certaines raies des éléments injectés peut s'expliquer par l'action des métastables de l'argon neutre et de l'argon ionisé. C'est pourquoi une méthode d'absorption atomique à deux longueurs d'onde a été mise au point qui permet d'effectuer la mesure des densités de métastables

Feasibility of UV laser ablation inductively coupled plasma atomic emission spectrometry for depth profiling of glass materials

No abstract availabl

Analysis of importance of road networks exposed to natural hazards

International audienceRoads in mountains areas are exposed to natural hazards such as snow avalanches, torrent floods and rockfalls. Risk depends both on hazard, direct and indirect vulnerability. In case of roads, the indirect vulnerability relates to the consequences of road closures which is rarely assessed. The criticality of these closures depends on the importance of road sections. A new methodology is proposed in the context of natural risks management in mountains. Based on structural networks analysis, it aims to assess the accessibility level of mountain territories and to identify critical roads sections depending both on their exposure to phenomenons but also on the importance of roads on economic, social, environmental contexts. The structural network analysis allows to describe how far the network properties conditions the accessibility from one point to another. This approach is combined to multicriteria decision making to assess importance according to economic, social or human factors but also fragility, resilience or risk sensitivity on road sections

Effect of operating conditions on excitation temperature and electron number density in axially-viewed ICP-OES with introduction of vapors or aerosols

none3The combined effect of the power and the carrier gas flow rate on excitation temperature, electron number density, ionic-to-atomic line intensity ratios and departure from local thermal equilibrium has been studied in an axially-viewed plasma with introduction of different amounts of wet aerosols, partially desolvated aerosols or dry vapours, according to empirical modelling and experimental design methods. Under robust conditions (1500 W and a carrier gas flow rate of 0.7–0.85 L/min), an increase in water loading led to an improvement in the plasma excitation properties, while desolvation caused degradation. In contrast, under non-robust conditions, the plasma was no longer able to tolerate an increase in water loading and desolvation resulted in an improvement in the plasma characteristics. The hydrogen formed during the hydride generation process significantly improved the plasma excitation properties, regardless of the conditions. In this instance, the plasma characteristics were primarily affected by the reductant concentration, which determined the amount of hydrogen generated, and by the carrier gas flow rate, which controlled its residence time within the plasma. In contrast, there was no relevant change in the plasma excitation conditions due to systematic variation of HCl concentration from 0.1 to 6 M.M. GROTTI; C. LAGOMARSINO; J.M. MERMETGrotti, Marco; C., Lagomarsino; J. M., Merme

COMPARISON OF A Nd : YAG LASER AND A XeCl LASER FOR THE ABLATION OF SOLIDS IN SPECTROCHEMICAL ANALYSIS

No abstract availabl

ARGON-TITANIUM HOLLOW CATHODE AFTERGLOW

The mechanisms of the energy transfer between metastable and ionic species of the rare gases and metallic atoms are responsible for the laser action in rare gas-metal vapor discharge. Knowledge of the mechanisms of the production and loss of the metallic species in a rare gas plasma is therefore very inportant. The pulsed afterglow technique has already been used to study the excited metallic ion production in He-Cd, He-Zn (1) and He-Pb (2) discharge. In these experiments, the discharge cell containing metal pellets is placed inside an oven to produce the metal vapor at desired pressure. But this technique cannot be used for the metals having a high boiling point. For example a density of 1011 atoms cm-3 is obtained at 210°C for Zinc but at 1300°C for Titanim