Search results for "raman scattering"
showing 10 items of 284 documents
High-resolution non-linear Raman spectroscopy in gases
1990
The resolution in the Raman spectra of gases has been greatly improved by the development of the different methods of non-linear Raman scattering. When two laser beams, one of which has a tunable frequency, are focused in a sample, a stimulated Raman process occurs as soon as the frequency difference between the two lasers is equal to a Raman-active rovibrational or rotational transition frequency. The Raman resonance can be detected in different ways: by coherent anti-Stokes Raman scattering (CARS) or the corresponding Stokes process (CSRS), by a gain in one of the beams (stimulated Raman gain spectroscopy, SRGS) or a loss in the other (inverse Raman spectroscopy, IRS), or even by detectio…
The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation
2016
After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repea…
Existence of two time scales in the phase transitions of BaTiO3
1991
Abstract We report new Raman scattering measurements in the tetragonal phase of a single domain BaTiO3 crystal. Data reveal the occurence of a large quasi elastic scattering. The Raman profile is analysed in terms of coexisting soft phonon and Debye relaxation.
Elastic scattering cross sections for 6Li and 7Li scattering by aluminum, silicon and titanium below 12 MeV at angles of 140∘ and 170∘
1999
Abstract Elastic scattering cross sections for 6Li and 7Li scattering by natural aluminum, silicon and titanium have been measured in the energy range of 4–11 MeV. Scattering angles were 140∘ and 170∘ for 6Li and 140∘ for 7Li. The threshold energies above which Rutherford backscattering becomes invalid have been determined. Above this threshold the cross sections decrease rapidly, rendering backscattering analysis impractical. For 7Li scattering by Al and Si the observed threshold values were higher than for 6Li scattering. This behavior was reversed for scattering by Ti. The findings were systematic for both scattering angles. The present cross section and threshold data have been compared…
Gold nanoparticles/electrochemically expanded graphite composite: A bifunctional platform toward glucose sensing and SERS applications
2019
Abstract An integrated nanogold/expanded graphite based sensor was fabricated by a former electrochemical etching of the pencil lead electrode (PLE) and a later in-situ deposition of gold nanoparticles (AuNPs). The electrochemical pretreatment of PLE (EPLE) created a 3D graphene-like surface, enhanced the electrode surface area and facilitated the electron transfer ability within 5 min without any hazardous chemicals added. The obtained AuNPs/EPLE sensor had an excellent electrochemical response to glucose with a wide linear concentration range, from 0.05 to 38 mM and 38 to 60 mM, and a low detection limit of 5 μM (S/N = 3). Furthermore, the AuNPs/EPLE sensor was successfully employed to de…
Splitting of surface-related phonons in Raman spectra of self-assembled GaN nanowires
2012
cited By 2; International audience; Micro Raman spectroscopy studies have been performed on GaN nanowires grown by Plasma-Assisted Molecular Beam Epitaxy on Silicon (111) substrate. From the analysis of experimental data, the emergence of a two peaks band located near 700 cm-1 has been attributed to the Raman scattering by surface-related phonons. We have analyzed the surface character of these two modes by changing the dielectric constant of the exterior medium and some experimental parameters. Furthermore, a theoretical model describing the nanowires ensemble by means of an effective dielectric function has been used to interpret the Raman scattering results. Those numerical simulations a…
Fiber-based device for the detection of low-intensity fluctuations of ultrashort pulses
2012
International audience; We describe a fiber-based device that can significantly enhance the low intensity fluctuations of an ultrashort pulse train to detect them more easily than with usual direct detection systems. Taking advantage of the Raman intrapulse effect that progressively shifts the central frequency of a femtosecond pulse propagating in an anomalous dispersion fiber, a subsequent spectral filtering can efficiently increase the level of fluctuations by more than one order of magnitude. We show that attention has to be paid to maintain the shape of the statistical distribution unaffected by the nonlinear process.
Nonrecursive multiple shock formation via four-wave mixing: theory and experiment
2002
We show theoretically and experimentally that a beat signal propagating along a normally dispersive fiber can trigger the formation of multiple shocks. This phenomenon critically depends on the input frequency separation and power of the beat signal.
High-pressure lattice dynamics in wurtzite and rocksalt indium nitride investigated by means of Raman spectroscopy
2013
We present an experimental and theoretical lattice-dynamical study of InN at high hydrostatic pressures. We perform Raman scattering measurements on five InN epilayers, with different residual strain and free electron concentrations. The experimental results are analyzed in terms of ab initio lattice-dynamical calculations on both wurtzite InN (w-InN) and rocksalt InN (rs-InN) as a function of pressure. Experimental and theoretical pressure coefficients of the optical modes in w-InN are compared, and the role of residual strain on the measured pressure coefficients is analyzed. In the case of the LO band, we analyze and discuss its pressure behavior considering the double-resonance mechanis…
Raman scattering in nanosized nickel oxide NiO
2007
Magnetic ordering in nanosized (100 and 1500 nm) nickel oxide NiO powders, prepared by the plasma synthesis method, was studied using Raman scattering spectroscopy in a wide range of temperatures from 10 to 300 K. It was observed that the intensity of two- magnon band decreases rapidly for smaller crystallites size. This effect is attributed to a decrease of antiferromagnetic spin correlations and leads to the antiferromagnetic-to- paramagnetic phase transition .