Detection of Elements at All Three r-process Peaks in the Metal-Poor Star HD 160617

We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundances or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.Comment: Published in the Astrophysical Journal (22 pages, 12 figures

A Spectroscopic study of laser-induced Tin-Lead plasma: transition probabilities for spectral lines of Sn I

In this paper, we present transition probabilities for 97 spectral lines of Sn I, corresponding to transitions n(n = 6,7,8)s → 5p2, n(n = 5,6,7)d → 5p2, 5p3 → 5p2, n(n = 7)p → 6s, determined by measuring the intensities of the emission lines of a Laser-induced breakdown (emission) spectrometry (LIBS). The optical emission spectroscopy from a laser-induced plasma generated by a 10 640 Å radiation, with an irradiance of 1.4 × 1010 Wcm− 2 on an Sn–Pb alloy (an Sn content of approximately 20%), in vacuum, was recorded at 0.8 µs, and analysed between 1900 and 7000 Å. The population-level distribution and corresponding temperature were obtained using Boltzmann plots. The electron density of the plasma was determined using well-known Stark broadening parameters of spectral lines. The plasma under study had an electron temperature of 13,200 K and an electron number density of 2 × 1016 cm− 3. The experimental relative transition probabilities were put on an absolute scale using the branching ratio method to calculate Sn I multiplet transition probabilities from available radiative lifetime data of their upper states and plotting the Sn I emission spectrum lines on a Boltzmann plot assuming local thermodynamic equilibrium (LTE) to be valid and following Boltzmann's law. The LTE conditions and plasma homogeneity have been checked. Special attention was paid to the possible self-absorption of the different transitions. The experimental results obtained have been compared with the experimental values given by other authors

La spondylarthrite ankylosante et les gens impliqués dans la maladie

RENNES1-BU Santé (352382103) / SudocLYON1-BU Santé (693882101) / SudocSudocFranceF

Etude d'une technique laser cube-capillaire pour la mesure d'indices de réfraction

BREST-BU Droit-Sciences-Sports (290192103) / SudocSudocFranceF

DETERMINATION DU COEFFICIENT D'ABSORPTION PAR L'ANALYSE TEMPORELLE DE LA RETRODIFFUSION

Nous présentons une méthode de mesure optique qui, par télédétection à partir de l'évolution temporelle du signal rétrodiffusé, permet de déterminer localement les caractéristiques du coefficient d'atténuation d'un milieu liquide. Cette méthode, qui suppose l'utilisation d'un laser impulsionnel et la résolution temporelle du signal diffusé à 180°, a été testée sur l'eau pure chargée de particules diffusantes et sur différents échantillons d'eau de mer

Experimental characterization of immersed targets by polar decomposition of the Mueller matrices

The possibility of characterizing immersed targets in laboratory conditions, whatever the water surface roughness is discussed in this paper. The first idea was to reduce the interface effects or better to suppress them within the analysis.We used the Mueller formalism to characterize targets in the laboratory. In optics, each element can be described by a Mueller matrix. Then, in the present work we tried to decompose the global measured matrix and to separate the interface matrix from the target matrix which is the one of interest. This paper shows it impossible to perform such a decomposition. We succeeded in reducing the interface effects without eliminating them entirely. So this paper focuses on finding a decomposition algorithm of a Mueller matrix to deduce the polarimetric type of a target whatever the interface state