Fluorescence induite par laser

Résumé

La fluorescence induite par laser est une méthode de diagnostic laser utilisée principalement pour la caractérisation d'écoulements fluides. On l'utilise également en chimie analytique pour le dosage des traces. L'avantage principal réside dans le fait qu'il s'agisse d'une méthode non intrusive, ce qui fait qu'elle est souvent employée pour la recherche en combustion pour la mesure de champs de température dans une flamme ou dans des gouttelettes de combustible. Outre un volume de mesure réduit (quelques \mu m^3), cette technique dispose d'une résolution temporelle importante et d'une excellente cohérence spatiale. Elle reste néanmoins d'une grande technicité et chère à mettre en œuvre. Principe physique La fluorescence induite par laser consiste en l'émission spontanée de photons par les molécules d'un traceur, à la suite de l'absorption d'un rayonnement laser accordé sur une transition de l'espèce sondée. Le principe de Franck-Condon illustrant le décalage

Source officielle

https://fr.wikipedia.org/wiki/Fluorescence_induite_par_laser

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The physical principles of laser light materials interactions are introduced with a large number of industrial application examples. Materials processing lasers are developing further and further, the lecture presents the physical limitations of the processes.

The aim of this course is to treat three of the major techniques for structural characterization of molecules: mass spectrometry, NMR, and X-ray techniques.

This course covers the main applications of micro devices for life science and biomedical applications. The course is organized by application topic. It is also covering the basic physical, biological, chemical, technological concepts, which are presented as transversal introductory section

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Dissociation threshold of H218O: Validating ab initio calculations by state-selective triple-resonance spectroscopy

We employ state-selective triple-resonance vibrational overtone spectroscopy for a direct measurement of the lowest dissociation energy, Do, in the (H2O)-O-18 molecule. The measured value of 41 154.22 +/- 0.25 cm(-1) is in an excellent agreement with that, predicted by ab initio theoretical calculations. This result validates the computations, adding more confidence to what this theory can predict for water. In addition, we have measured the required for this experiment energy levels of (H2O)-O-18 in the region near 27 000 cm(-1), as well as the laser-induced fluorescence (LIF) spectrum of the (OH)-O-18 isotopologue, for which near 60 electronic transitions have been assigned. (C) 2015 Elsevier B.V. All rights reserved.

Elsevier2015

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State-to-state studies of intramolecular energy transfer in highly excited HOOH(D): Dependencies on vibrational and rotational excitation

Thomas Rizzo

We use infrared-optical double resonance excitation, together with laser induced fluorescence (LIF) product detection, to measure rotationally resolved vibrational overtone spectra of hydrogen peroxide at energies up to 4500 cm(-1) above the O-O dissociation threshold. The spectroscopic constants obtained from such spectra help characterize the potential energy surface and provide a stringent test for any theoretical representation thereof. Line profiles of individual rovibrational features provide information on the vibrational and rotational dependence of the intramolecular dynamics. Coupling to the manifold of optically inactive background states is independent of the total density of rovibrational states but rather controlled by specific low-order coupling terms in the Hamiltonian. Moreover, we find no significant difference in the IVR dynamics between states with all quanta in a single OH oscillator or distributed between the two local OH stretches. Finally, increasing rotation around the O-O pseudo-figure axis clearly enhances the IVR rate in most vibrational bands of H2O2 due to increased a-axis Coriolis coupling. Comparison to other OH stretch containing molecules allows us to define chromophore specific dynamics of this light atom oscillator. (C) 2000 American Institute of Physics. [S0021-9606(00)01517-8].

2000

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, ,

We describe the design and performance tested during six years of clinical trials of a fluorescence endoscope for the detection and delineation of cancers in several hollow organs. The apparatus is based on the imaging of the laser-induced fluorescence that differs between a tumor and its surrounding normal tissue. The tests are carried out in the upper aerodigestive tract, the tracheobronchial tree, the esophagus, and the colon. In the three former cases an exogenous dye is used (Photofrin II), whereas in the latter case fluorescein molecules conjugated with monoclonal antibodies directed against carcinoembryonic antigen are injected. The decrease of native tissue autofluorescence observed in early cancers is also used for detecting lesions in the tracheobronchial tree. The fluorescence contrast between the tumor and surrounding normal tissue is enhanced by real time image processing. This is done by simultaneously recording the fluorescenceimage in two spectral domains, after which these two images are digitized and manipulated with a mathematical operator (look-up table) at video frequency. Moreover, the device that is described below allows for an immediate observation of the endoscopic area under white light illumination during fluorescence detection in order to localize the origin of the “positive” fluorescence signals. Typical results obtained in the tracheobronchial tree and in the colon are presented and the sources of false positives and false negatives are evaluated in terms of the fluorescent dye, tissue optical properties, and illumination optics.

1997

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