Search results for "SPECTRA"
showing 10 items of 3542 documents
Symmetry and Electronic Structure of Noble Metal Nanoparticles and the Role of Relativity
2004
High resolution photoelectron spectra of cold mass selected Cu_n-, Ag_n- and Au_n- with n =53-58 have been measured at a photon energy of 6.42 eV. The observed electron density of states is not the expected simple electron shell structure, but seems to be strongly influenced by electron-lattice interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a direct consequence of their icosahedral symmetry, as is confirmed by density functional theory calculations. Neighboring sizes exhibit perturbed electronic structures, as they are formed by removal or addition of atoms to the icosahedron and therefore have lower symmetries. Gold clusters in the same size range show complet…
Temperature Distribution of a Non-flaring Active Region from Simultaneous Hinode XRT and EIS Observations
2011
We analyze coordinated Hinode XRT and EIS observations of a non-flaring active region to investigate the thermal properties of coronal plasma taking advantage of the complementary diagnostics provided by the two instruments. In particular we want to explore the presence of hot plasma in non-flaring regions. Independent temperature analyses from the XRT multi-filter dataset, and the EIS spectra, including the instrument entire wavelength range, provide a cross-check of the different temperature diagnostics techniques applicable to broad-band and spectral data respectively, and insights into cross-calibration of the two instruments. The emission measure distribution, EM(T), we derive from the…
Corrigendum: Fabrication and heating rate study of microscopic surface electrode ion traps
2012
We report heating rate measurements in a microfabricated goldon-sapphire surface electrode ion trap with a trapping height of approximately 240 μm. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation, the heating rates increase by approximately one order of magnitude. The increase in heating rates is largest in the ion-loading region of the trap, providing a strong hint that surface contamination plays a major role for excessive heating rates. We discuss data found i…
Primordial Black Holes and Slow-Roll Violation
2017
For primordial black holes (PBH) to be the dark matter in single-field inflation, the slow-roll approximation must be violated by at least ${\cal O}(1)$ in order to enhance the curvature power spectrum within the required number of efolds between CMB scales and PBH mass scales. Power spectrum predictions which rely on the inflaton remaining on the slow-roll attractor can fail dramatically leading to qualitatively incorrect conclusions in models like an inflection potential and misestimate the mass scale in a running mass model. We show that an optimized temporal evaluation of the Hubble slow-roll parameters to second order remains a good description for a wide range of PBH formation models …
XMM-Newton spectroscopy of the metal depleted T Tauri star TWA 5
2005
We present results of X-ray spectroscopy for TWA 5, a member of the young TW Hydrae association, observed with XMM-Newton. TWA~5 is a multiple system which shows Halpha emission, a signature typical of classical T Tauri stars, but no infrared excess. From the analysis of the RGS and EPIC spectra, we have derived the emission measure distribution vs. temperature of the X-ray emitting plasma, its abundances, and the electron density. The characteristic temperature and density of the plasma suggest a corona similar to that of weak-line T Tauri stars and active late-type main sequence stars. TWA 5 also shows a low iron abundance (~0.1 times the solar photospheric one) and a pattern of increasin…
Multiwavelength observations of the Be/X-ray binary 4U1145-619
1997
We report optical and infrared observations of the massive X-ray binary system 4U1145-619 (V801 Cen) which show that the circumstellar disc of the Be star component is in decline. Infrared J,H,K,L magnitudes of V801Cen have been monitored from 1993 March to 1996 April. H alpha spectra have been obtained throughout the same period. We find that both the infrared excess and the Balmer emission have been in decline throughout the period of observations. A 13 year optical and X-ray history of the source has been collated, revealing a possible correlation between the optical and X-ray activity. In addition, we have used u,v,b,y,beta indices, corrected for both circumstellar and interstellar effe…
Deep X-ray survey of the young open cluster NGC 2516 with XMM-Newton
2006
We report on a deep X-ray survey of the young (~ 140 Myr), rich open cluster NGC 2516 obtained with the EPIC camera on board the XMM-Newton satellite. By combining data from six observations, a high sensitivity, greater than a factor 5 with respect to recent Chandra observations, has been achieved. We detected 431 X-ray sources and 234 of them have as optical counterparts cluster stars spanning the entire NGC 2516 Main Sequence. The X-ray luminosities of cluster stars span the range log Lx (erg/s) = 28.4 - 30.8. The representative temperatures span the 0.3 - 0.6 keV (3.5 - 8 MK) range for the cool component and 1.0 - 2.0 keV (12 -- 23 MK) for the hot one; similar values are found in other y…
Spectroscopic observations of blue stars with infrared excesses in NGC 6611
2013
The young open cluster NGC 6611 includes among its candidate members a class of peculiar objects with interesting properties: blue stars with infrared IR excesses. These stars show excesses in IR bands, signature of the presence of a circumstellar disk, but optical colors typical of older field stars. In order to confirm their membership to the cluster, it is therefore important to use new spectroscopic observations, together with previous photometric data. We aim at confirming the membership of these objects and at investigating their physical properties to verify whether the observed colors are intrinsic or altered by the presence of the disk or by the accretion processes. We analyze the …
High-resolution IR spectrum of AsH2D: Ro-vibrational analysis of the bending triad bands , , and
2008
Abstract The infrared spectrum of the AsH2D molecule has been measured in the region of the three bending fundamental bands on a Fourier transform spectrometer with a resolution of 0.0024 cm−1 and analyzed for the first time. More than 7500 normally allowed and in addition about 600 forbidden, but perturbation-activated transitions with J max = 21 , K a max = 20 and K c max = 21 have been assigned to the bands ν 3 , ν 4 , and ν 6 . The measured transition wavenumbers were used to determine 1047 upper energy values. These energies were fitted with a Watson-type Hamiltonian in A reduction and IIIl representation taking into account resonance interactions between all three bending states, (001…
Analysis of the Infrared Fourier Transform Spectrum of the Spectra of Silane in the Range 2930-3300 cm(-1).
1999
The infrared spectrum of (28)SiH(4) between 2930 and 3300 cm(-1) was recorded using the Laboratoire de Physique Moleculaire et Applications (LPMA.) Fourier transform spectrometer. The instrumental response function width chosen makes it possible to obtain a Doppler-limited spectrum. The observed spectrum belongs to the tetrad built with one quantum of stretching mode (nu(1) or nu(3)) and one quantum of bending mode (nu(2) or nu(4)). The excited states are formed from eight vibrational sublevels: nu(1) + nu(2)(E), nu(1) + nu(4)(F(2)), nu(2) + nu(3)(F(1) + F(2)), and nu(3) + nu(4)(A(1) + E + F(1) + F(2)). The intricacy of the upper states was resolved using the variations of the line strength…