Search results for "broadening"
showing 10 items of 95 documents
Correlation between optical properties and barrier composition in InxGa1−xP/GaAs quantum wells
1998
9 páginas, 11 figuras.
Experimental signature of optical wave thermalization through supercontinuum generation in photonic crystal fiber
2009
International audience; We report an experimental, numerical and theoretical study of the incoherent regime of supercontinuum generation in a two zero dispersion wavelengths fiber. By using a simple experimental setup, we show that the phenomenon of spectral broadening inherent to supercontinuum generation can be described as a thermalization process, which is characterized by an irreversible evolution of the optical field towards a thermal equilibrium state. In particular, the thermodynamic equilibrium spectrum predicted by the kinetic wave theory is characterized by a double peak structure, which has been found in quantitative agreement with the numerical simulations without adjustable pa…
Line broadening coefficient calculations for methane perturbed by nitrogen
2010
Abstract We report semiclassical line broadening calculations for methane perturbed by nitrogen at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for nitrogen) and atom–atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions. As a consequence, a combination of symbolic computation and source code generation was employed to implement practical calc…
Calculated line broadening parameters for methane perturbed by diatomic molecules
2013
International audience; We report semiclassical line broadening calculations for methane perturbed by diatomic molecules: nitrogen, N2, oxygen, O2 and hydrogen, H2, at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for the diatomic molecules) and atom-atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions in the case of N2 and O2. For H2, a lower…
Experimental and theoretical studies of Stark profiles of Ar I 696.5 nm spectral line in laser-induced plasma
2019
Abstract We report the results of the Stark profile studies of the 696.543 nm Ar I spectral line in laser-induced plasma generated by a nanosecond Nd:YAG laser radiation at 532 nm in argon at reduced pressure. Plasma diagnostics was performed with the use of the laser Thomson scattering method, free from assumptions about the plasma thermodynamic equilibrium, its composition but also independently of plasma emission spectra. The profiles were investigated in wide range of electron densities and temperatures, from 2.81 · 1022 m − 3 to 5.69 · 1023 m − 3 and from 10 430 K to 73 400 K, respectively. Stark profiles were calculated using a semi-classical method as well as by N-body numerical simu…
Helium and Argon Line Broadening in the nu2 Band of CH4
2004
Abstract The spectra of the gaseous mixtures CH 4 –He and CH 4 –Ar were obtained in the spectral region 1400–1750 cm −1 with a resolution up to 0.003 cm −1 . Helium and argon pressure broadenings for the vibration–rotation lines of the ν 2 band of CH 4 have been estimated at room temperature for some lines in the P , Q , and R branches. These values were also calculated using the theoretical approach developed by Robert and Bonamy, extended to the case of tetrahedral molecules. The helium data have been found to be in a satisfactory agreement whereas a divergence of calculated and measured broadening coefficients has been evidenced in the case of argon. Simulations of the ν 2 band shapes of…
Estimation of line parameters under line mixing effect: the nu3 band of CH4 in helium
2001
International audience; Spectra of CH4-He mixtures were measured in the P and R branch regions of nu3 vibration-rotation band at lower pressures of 0.26-1.0 bar and for the whole band at higher pressures up to 90 bar. The line broadening coefficients were found from lower pressure data for the lines of the P branch. These coefficients were calculated in the framework of the Robert and Bonamy semi-classical approach. In general, they agree with the experimental ones, but a small J-dependent deviation was observed. Line mixing effects were observed at all pressures. At higher pressures they were interpreted in terms of the adjusted branch-coupling model. At lower pressures line mixing effects…
Positronics of radiation-induced effects in chalcogenide glassy semiconductors
2015
Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.
Positron annihilation probing of crystallization effects in TAS-235 glass affected by Ga additions
2014
Abstract Crystallization effects in Te20As30Se50 glass known also as TAS-235 affected by Ga additions to Ga2Te20As28Se50 and Ga5Te20As25Se50 compositions are probed with positron annihilation spectroscopy in the measuring modes exploring positron lifetimes and Doppler broadening of annihilation line. Occurring of cubic-phase Ga2Se3 droplets with character nanoscale sizes in partially-crystallized Ga2Te20As28Se50 alloy is shown to be associated with agglomeration of intrinsic free-volume voids, this process being enhanced over microcrystalline scale in Ga5Te20As25Se50 alloy. Crystallization changes in the void structure of TAS-235 glass are considered in terms of free-volume evolution under …
Defects in Martensitic Stainless Steel 1.4031 (EN) Exposed to Friction as Seen by Positron Annihilation
2010
We present experimental results of measurements of the Doppler broadening of annihilation line and positron annihilation lifetimes in martensitic stainless steel 1.4031 (EN) samples exposed to the dry sliding under different loads. In particular, we tested the subsurface zone under the worn surfaces. As a main result, we obtained information about the defect profiles in this zone and the total extent of the damage region induced by the dry sliding.