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Doppler broadening

About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.


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Journal ArticleDOI
TL;DR: In this article, a positron annihilation study of defects created in Si by rf hydrogen plasminar exposure at 275°C was performed, and the Doppler broadening parameter for the annihilation gamma rays was strongly correlated with the hydrogen coverage of the void surfaces.
Abstract: We report a positron annihilation study of defects created in Si by rf hydrogen‐plasma exposure at 275 °C. Analysis of positron annihilation spectroscopy data indicates voidlike structures in a defective ayer extending to ≊14 nm from the surface at a concentration of 1.9±0.5×1020 cm−3. The Doppler broadening parameter for the annihilation gamma rays is strongly correlated to the hydrogen coverage of the void surfaces, voids remain in the Si to at least 800 °C while the hydrogen is desorbed from their surfaces between 600 and 800 °C.

33 citations

Journal ArticleDOI
TL;DR: In this paper, the first observation of saturation broadening in a high-resolution coherent Raman spectrum of the v 2 Q-branch of acetylene was reported, which is significantly greater than the calculated ac Stark broadening of less than 100 MHz.

33 citations

Journal ArticleDOI
TL;DR: In this article, the influence of the spectral width on the modulation behavior of semiconductor injection lasers has been investigated theoretically on the basis of multimode rate equations and analytical expressions are derived yielding an effective rate of spontaneous emission for a suitable description of dynamic characteristics of injection lasers.
Abstract: The influence of the spectral width on the modulation behaviour of semiconductor injection lasers has been investigated theoretically on the basis of multimode rate equations. Analytical expressions are derived yielding an effective rate of spontaneous emission for a suitable description of dynamic characteristics of injection lasers. This effective emission rate may drastically exceed the total rate of spontaneous emission into the lasing modes. In the case of large signal modulation it has been shown that a large modulation depth as required for PCM-transmission also yields a considerable spectral broadening.

33 citations

Journal ArticleDOI
TL;DR: In this article, the authors considered the problem of non-coherent scattering in a spectral line for an arbitrary redistribution law, and proposed new methods for solving radiative transfer integro.
Abstract: The paper is devoted to the consideration of the problems of non-coherent scattering in a spectral line for an arbitrary redistribution law. The representation of the redistribution function r(x′,x) in the form r(χ′,χ) = ∑ k = 1 ∞ A k α k (χ′)α k (χ) is used to study the various mechanisms of line broadening. The form of representation plays an important role in this investigation. New methods for solving radiative transfer integro—differential equations, as well as the corresponding integral equations are suggested. The solution of integral equations involves factorization of matrix integral operators. The generalized classical problems of absorption-line formation in stellar atmospheres are formulated and solved (Shuster's and Eddington's models). The results of numerical calculations, carried out to the fourth order, are given for Doppler broadening.

33 citations

Journal ArticleDOI
TL;DR: In this article, a quantum cascade distributed feedback laser (QC-DFB) operating continuous wave (cw) at ~100 K is frequency modulated at f = 10 kHz and locked to the center of a transition at 1921 cm-1 in the fundamental band of NO.
Abstract: Measurements of NO concentrations at sub-ppm levels in vehicle exhaust are needed for emissions certification of future ultra-low emission vehicles. We demonstrate a wavelength-modulation, laser-based, NO detection system suitable for this purpose. A quantum cascade distributed feedback laser (QC-DFB) operating continuous wave (cw) at ~100 K is frequency modulated at f = 10 kHz and locked to the center of a transition at ~1921 cm-1 in the fundamental band of NO. The demodulated signal at 2f of the beam passing through the sample cell directly measures the NO concentration. The cell is a multipass Herriott-type with a 100-m path length. Doppler broadening, pressure broadening, and unresolved L doubling combine to yield a pressure for optimum sensitivity of 100 torr and a modulation amplitude of ~600 MHz. A flowing gas system is used to avoid problems with adsorption and desorption of NO from the cell walls. The reduced pressure eliminates interference from other gas species. Detection of NO concentrations in the few parts-per-billion (ppb) range is demonstrated in diluted exhaust-gas bag samples collected in the vehicle certification process.

33 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202331
202290
2021122
2020134
2019128
2018122