Search results for "SPECTRA"

Three-dimensional mapping and range measurement by means of projected speckle patterns.

2008

We present a novel approach for three-dimensional (3D) measurements that includes the projection of coherent light through ground glass. Such a projection generates random speckle patterns on the object or on the camera, depending if the configuration is transmissive or reflective. In both cases the spatially random patterns are seen by the sensor. Different spatially random patterns are generated at different planes. The patterns are highly random and not correlated. This low correlation between different patterns is used for both 3D mapping of objects and range finding.

Multimodal reflectivity of CRIGF filters: First experimental observation and modelling

2015

International audience; Cavity Resonator Integrated Guided-mode Resonance Filter (CRIGF) are a new class of filtering reflectors whose selected wavelength and spectral width are independent of the angle of incidence unlike GMRF. These particular properties allow both compactness and a high angular acceptance. However, ours studies show that CRIGFs offer simultaneously spectral and modal filtering and we evidence high-spatial-order reflected modes. In this paper, we will present characterization of the spectral and spatial profile that demonstrates the existence of these high-order modes. In addition, we will present a model based on the physical understanding of implied phenomena to explain…

Gap solitons and modulation instability in a dynamic Bragg grating with nonlinearity management

2008

International audience; We investigate the occurrence of modulation instability in systems in which a dynamic Bragg grating consists of alternating positive and negative Kerr coefficients. The dependence of modulation instability gain spectra over the perturbation wavenumber and system parameters is portrayed near and at the edges of the photonic band gap structure. Further, we demonstrate the generation of traveling gap solitons near the photonic band gap structure through the modulation instability

The Gaia-ESO Survey: Catalogue of Hα emission stars

2015

We discuss the properties of Hα emission stars across the sample of 22035 spectra from the Gaia-ESO Survey internal data release, observed with the GIRAFFE instrument and largely belonging to stars in young open clusters. Automated fits using two independent Gaussian profiles and a third component that accounts for the nebular emission allow us to discern distinct morphological types of Hα line profiles with the introduction of a simplified classification scheme. All in all, we find 3765 stars with intrinsic emission and sort their spectra into eight distinct morphological categories: single-component emission, emission blend, sharp emission peaks, double emission, P-Cygni, inverted P-Cygni…

Rotational spectra of CF+and13CF+: accurate rest frequencies and spectroscopic parameters

2010

Context. The astrophysical relevance of the fluoromethylidynium ion and its importance for the interstellar chemistry of fluorine motivated the present laboratory spectroscopic investigation of both 12 CF + and the corresponding 13 C-containing isotopologue, 13 CF + . Aims. This investigation has been carried out to provide accurate rest frequencies for future (radioastronomical) observations, to improve the accuracy of the values for the spectroscopic parameters available in the literature for CF + , and to provide them for the first time for 13 CF + . Methods. Rotational spectra of CF + and 13 CF + were recorded in the millimeter- and submillimeter-wave frequency ranges. Their investigati…

Line Identification of Atomic and Ionic Spectra of Holmium in the Visible Spectral Range. I. Spectrum of Ho i

2019

Wavelength dependence of multiphoton ionization of xenon

2004

We have studied the multiphoton ionization of xenon atoms by $160\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$ pulses at intensities of $5\ifmmode\times\else\texttimes\fi{}{10}^{12}$ and $1.3\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.3em}{0ex}}\mathrm{W}∕{\mathrm{cm}}^{2}$ and present photoelectron kinetic energy and angular distribution spectra measured with a photoelectron imaging spectrometer. A noncollinear optical parametric amplifier allows us to tune the wavelength of the laser pulse over a range between 500 and $700\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. Resonant and nonresonant processes as well as channel switching effects have been observed in this intensity and wavel…

The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project

2005

We use the data of the Chandra Orion Ultradeep Project (COUP) to study the nearly 600 X-ray sources that can be reliably identified with optically well characterized T Tauri stars (TTS) in the Orion Nebula Cluster. We detect X-ray emission from more than 97% of the optically visible late-type (spectral types F to M) cluster stars. This proofs that there is no ``X-ray quiet'' population of late-type stars with suppressed magnetic activity. All TTS with known rotation periods lie in the saturated or super-saturated regime of the relation between activity and Rossby numbers seen for main-sequence (MS) stars, but the TTS show a much larger scatter in X-ray activity than seen for the MS stars. S…

Results from Droxo

2007

AIMS. We study the variability of the Fe 6.4 KeV emission line from the Class I young stellar object Elias 29 in the Rho-Oph cloud. METHODS. We analysed the data from Elias 29 collected by XMM during a nine-day, nearly continuous observation of the Rho-Oph star-forming region (the Deep Rho-Oph X-ray Observation, named Droxo). The data were subdivided into six homogeneous time intervals, and the six resulting spectra were individually analysed. RESULTS. We detect significant variability in the equivalent width of the Fe 6.4 keV emission line from Elias 29. The 6.4 keV line is absent during the first time interval of observation and appears at its maximum strength during the second time inter…

Chandra X-ray observations of the stellar group near the Herbig Be star MWC 297

2006

We present a Chandra ACIS-I X-ray observation of the region near the Herbig early-Be star MWC 297, where we detect a tight group of point X-ray sources. These are probably physically associated to MWC 297, because of their obvious clustering with respect to the more scattered field-source population. These data are compared to earlier ASCA data with much poorer spatial resolution, from which the detection of strong quiescent and flaring emission from MWC 297 itself was claimed. We argue that this star, contributing only 5% to the total X-ray emission of the group, was probably not the dominant contributor to the observed ASCA emission, while the X-ray brightest star in the group is a much b…