Search results for "Spectra"
showing 10 items of 3542 documents
D2hTDS-ST Software for Stark Spectrum Simulation of X2Y4 Asymmetric-Top Molecules
2011
Abstract We present the D 2 h TDS-ST ( D 2 h -Top Data System for Stark effect) program suite with the aim to simulate Stark spectra of any IR active rovibrational polyad of X 2 Y 4 ( D 2 h ) asymmetric-top molecules. D 2 h TDS-ST consists in a series of FORTRAN programs called by scripts. For calculation of Stark spectra, we obtained the expressions of the dipole moment and polarizability operators of X 2 Y 4 molecules using a tensorial formalism. For convenience, we integrated the D 2 h TDS-ST programs into the D 2 h TDS package. The D 2 h TDS suite (including the D 2 h TDS-ST programs) is freely available at the URL: http://icb.u-bourgogne.fr/OMR/SMA/SHTDS/D2HTDS.html .
Testing a portable laser-induced breakdown spectroscopy system on geological samples.
2012
9 pages; International audience; This paper illustrates the potentialities of a home-made portable LIBS (laser-induced breakdown spectroscopy) instrument in Earth sciences, more particularly in geochemically recognizing (i) tephra layers in lacustrine sediments and (ii) fossilization processes in ammonites. Abundances for selected lines of Al, Ca, Fe, Ti, Ba and Na were determined in lacustrine chalk sediments of the Jura, where the Laacher See Tephra (LST) layer is recorded. A statistical treatment of elemental maps produced from the section of a sedimentary column containing the LST event allows instrumental conditions to be optimized. Accumulating spectra from close shot positions gives …
A Galerkin approach for power spectrum determination of nonlinear oscillators
2002
A numerical method to estimate spectral properties of nonlinear oscillators with random input is presented. The stationary system response is expanded into a trigonometric Fourier series. A set of nonlinear algebraic equations, solved by Newton's method, leads to the determination of the unknown Fourier series coefficients of single samples of the response process. For cubic polynomial nonlinearities, closed-form expressions are used to find the nonlinear terms at each step of the solution scheme. Further, a simple procedure yields an approximation of an arbitrary nonlinearity by a cubic polynomial. Power spectral density estimates for the response process are constructed by averaging the s…
CROSS-POWER SPECTRAL DENSITY AND CROSS-CORRELATION REPRESENTATION BY USING FRACTIONAL SPECTRAL MOMENTS
2012
Core hole screening and decay rates of double core ionized first row hydrides.
2013
Because of the high intensity, X-ray free electron lasers allow one to create and probe double core ionized states in molecules. The decay of these multiple core ionized states crucially determines the evolution of radiation damage in single molecule diffractive imaging experiments. Here we have studied the Auger decay in hydrides of first row elements after single and double core ionization by quantum mechanical ab initio calculations. In our approach the continuum wave function of the emitted Auger electron is expanded into spherical harmonics on a radial grid. The obtained decay rates of double K-shell vacancies were found to be systematically larger than those for the respective single …
Inhomogeneous free-electron distribution in InN nanowires: Photoluminescence excitation experiments
2010
Photoluminescence excitation (PLE) spectra have been measured for a set of self-assembled InN nanowires (NWs) and a high-crystalline quality InN layer grown by molecular-beam epitaxy. The PLE experimental lineshapes have been reproduced by a self-consistent calculation of the absorption in a cylindrical InN NW. The differences in the PLE spectra can be accounted for the inhomogeneous electron distribution within the NWs caused by a bulk donor concentration $({N}_{D}^{+})$ and a two-dimensional density of ionized surface states $({N}_{ss}^{+})$. For NW radii larger than 30 nm, ${N}_{D}^{+}$ and ${N}_{ss}^{+}$ modify the absorption edge and the lineshape, respectively, and can be determined f…
First Specifications of a PSTM Working In the Infrared
1993
One of the most promising extension of the photon scanning tunneling microscope (PSTM) is its use as a locally resolved spectroscopic tool. The infrared (IR) spectral window offers a wide variety of interesting applications since many materials have a well-defined signature in this range. We have undertaken the experimental modifications that are necessary to operate the existing PSTM’s in the IR domain. In this work, we present preliminary data obtained with two IR light sources: an extended source (Globar type) and the free electron IR laser source (CLIO) available at LURE (Orsay). In both cases, the evanescent field has been detected with a fluoride glass optical fiber and the characteri…
The influence of the propagation path length on the results of the time–frequency analysis of the acoustic emission generated by partial discharges i…
2006
The paper presents the measurement results of the acoustic emission (AE) signals generated by partial discharges (PDs) at various thickness of the oil insulation layer. For the AE signals registered the time - frequency analysis was carried out based on the use of the short-time Fourier transform (STFT). Two- and three-dimensional spectrograms of the power spectrum density and the amplitude spectrum were determined. The evaluation of the influence of the propagation path length of the AE signal on the results of the time - frequency analysis was performed through the analysis of the spectrograms determined.
A new Frequency Domain Measure of Causality based on Partial Spectral Decomposition of Autoregressive Processes and its Application to Cardiovascular…
2019
We present a new method to quantify in the frequency domain the strength of directed interactions between linear stochastic processes. This issue is traditionally addressed by the directed coherence (DC), a popular causality measure derived from the spectral representation of vector autoregressive (AR) processes. Here, to overcome intrinsic limitations of the DC when it needs to be objectively quantified within specific frequency bands, we propose an approach based on spectral decomposition, which allows to isolate oscillatory components related to the pole representation of the vector AR process in the Z-domain. Relating the causal and non-causal power content of these components we obtain…
Frequency comb generation in whispering gallery mode silica microsphere resonators
2021
Optical frequency combs (OFC) using different kinds of whispering-gallery-mode (WGM) microresonators have already shown different applications and especially their applications in fiber optical communication systems as replacements of laser-arrays. For this application the free spectral range (FSR) of 200 GHz or less is desirable. Besides the fabrication material for microspheres, the resonator radius can be modified to change the FSR. In this paper use of silica microspheres for OFC represents an inexpensive alternative over the other microcombs: microring, microdisk, and microtoroid. We experimentally present a microsphere fabrication process from a different kind of silica (SiO2) fibers …