Search results for "COPI"
showing 10 items of 2618 documents
Simulation de spectres à haute température : une approche statistique du compromis résolution / précision
2010
International audience; Malgré les progrès continus enregistrés dans le domaine de la spectroscopie moléculaire, théorique et expérimentale, les banques de données spectroscopiques disponibles présentent des lacunes importantes, notamment pour l'interprétation des observations des environnements astrophysiques à haute température. Ce constat s'applique en particulier à la molécule de méthane présente dans les atmosphères de nombreux objets astrophysiques. La modélisation du coefficient d'absorption du méthane dans le proche infrarouge et/ou à haute température continue à défier les théoriciens du fait de la complexité intrinsèque de son spectre rovibrationnel. De fait, les analyses à haute …
Analyse locale des sensibilités des lectures angulaires, spectroscopiques et ellipsométriques de la Résonance des Plasmons de Surface en vue de la mi…
2006
The fluorescence labelling, used by the fluorescence biochips, is known to change the charge distribution of the labelled molecules and then modify their biological activity. Among label free biosensors, we choose an optical detection, such as spectroscopic ellipsometry and/or surface plasmon resonance (SPR) of the biolayers.These optical techniques are based on the measurement of both thickness and optical index of the adsorbed biolayer. An AFM statistical measurement of the thickness of functionalized lithographed microstructures has been performed in order to determine the thickness of the biolayers.We have shown that the spectroscopic reading of the SPR phase shift is 100 times more sen…
Identification of the contaminants present on the surface of lactose for pharmaceutical use and analysis of the impact of their presence on the inter…
2018
The discovery of the problem will go through training techniques at the nanoscale characterization and chemical analysis, the discovery of the industrial problem in society Armor Proteins, the validation of a pharmaceutical lactose. With the aim to increase our knowledge on powders for food or pharmaceutical use, we propose to study the effect of manufacturing processes, shaping, granulation on the reactivity of powders. The first part is devoted to the effect of purity on interactions-Lactose Lactose and Lactose-API measured / quantified by near-field techniques (AFM, SMM, MSAFM) under ambient atmosphere and under stressful conditions storage. Deriving a second portion of the preceding par…
Atomic Transitions and Population Control by Laser Frequency Scanning Speed and Magnetic Field
2022
In this thesis the influence of laser radiation and external uniform magnetic field on alkali-metal atomic vapor is studied. We focused on three topics. In the first part, we examined atomic population control in an M-type system to demonstrate that such systems can serve as universal three-bit logical devices. The second part concerns an experiment of atomic spectroscopy. From the fluorescence spectra recorded for stationary, transient and non-stationary interaction regimes, we were able to extract important parameter values which are the relaxation rate of the lower energy levels to the equilibrium isotropic state, the diffusion coefficient in a buffered vapor cell, and the corresponding …
Far-field imaging of the electromagnetic local density of optical states.
2008
International audience; We introduce a new experimental method to measure the local electromagnetic density of states (LDOS) by integrating the differential scattering cross section. The signal detected essentially reflects the intrinsic scattering response of the photonic structures and renders the partial LDOS dominated by evanescent modes. We give a theoretical understanding of the LDOS image formation and show a qualitative agreement between experimental images and theoretical maps. This approach can be practically applied to the direct measurement of an optical antenna's scattering efficiency and can provide valuable information for designing optimum structures utilized in radiative de…
Surface plasmon polaritons on metal cylinders with dielectric core
2001
International audience; Metal-cladded dielectric cylinders with submicron diameters may serve to model coated tips used in nearfield scanning optical microscopy. The signal measured may be greatly influenced by resonance effects due to eigenmodes of the probe. Especially, using a photon scanning tunneling microscope setup, gold-coated tips have been found to detect a signal proportional to the magnetic field distributions [E. Devaux et al.. Phys. Rev. B 62, 10 504 (2000)]. This effect is attributed to cylindrical surface plasmons. We present here fully retarded calculations of the dispersion and field patterns of the nonradiative plasmon modes in cylindrical geometry. We study the effect of…
Study of optical and magneto-optical processes in cesium, rubidium and potassium micro- and nano-metric thin atomic layers
2016
It has been investigated the D1 line transitions of 39K atoms in external magnetic fields using nanocells for the cases of sigma+ and pi polarizations of laser radiation. For the first time it is demonstrated the decoupling of electronic total angular momentum J and nuclear momentum I (complete hyperfine Paschen-Back regime) in external magnetic field. For 39K the decoupling takes place at B >> 165 G. In the case of linear polarization it is shown that for B > 400 G the transmission spectrum consists of 2 groups of transitions and each group contains of one so-called "Guiding transition" (GT). The GT indicates the asymptotic value of all transitions probabilities in the group and the freque…
Local detection of the optical magnetic field in the near zone of dielectric samples
2000
International audience; We present a study of the influence of the probe composition on the formation of constant-height photon scanning tunneling microscope images when observing a dielectric sample. Dramatic effects due to the metallization of the tip are presented and discussed in detail. We show how the recorded images can look quite different when the probe is dielectric or coated with gold. Comparison with numerical calculations indicate that the experimental signals are of electric or magnetic nature depending on the composition of the tip. For well-defined conditions, gold-coated tips provide images of the distribution of the magnetic field intensity associated with the optical near…
Formation of narrow optical resonances in thin atomic vapor layers of Cs, Rb, K and applications.
2019
This thesis presents the study of coherent light interaction with a sub-wavelength atomic alkali vapor layer confined in a nano-cell and applications for the formation of narrow optical resonances.We develop a theoretical model describing the resonant interaction of the laser light with the thin alkali vapor layer in the presence of an external static magnetic field. We show that due to a transient regime of interaction, only slow atoms contribute to the signal and their transmission spectrum is essentially Doppler-free. The nature of the obtained spectra makes the transmission spectroscopy from a nano-cell a convenient technique to perform studies of closely-spaced atomic transitions and i…
Study of supercontinuum sources based on tellurite glass optical fibers for mid-infrared absorption spectroscopy applied to gas sensing
2015
This work focuses on the development of mid-infrared supercontinuum light sources and their application for gas detection through absorption spectroscopy. The study of supercontinuum sources is based on nonlinear ultrashort pulse propagation in tellurite glass (80TeO2-10ZnO-10Na2O) and used in three different forms, namely a thin bulk sample, a microstructured suspended-core fiber, and a tapered suspended-core fiber. These technical means adapt themselves to distinct laser sources commercially available, thus optimizing the implementation of ultrawide-band infrared light sources. Experimental observations are compared to corresponding numerical simulations, thus pointing out the different u…