Theory of Resonance Broadening Including the Duration of Collision Effects

1975 ◽  
Vol 53 (1) ◽  
pp. 76-83 ◽  
Author(s):  
H. R. Zaidi
Keyword(s):  
Fourier Transform ◽  
Kinetic Theory ◽  
Line Shape ◽  
Average Duration ◽  
Collision Operator ◽  
Binary Collision ◽  
Static Limit ◽  
The Fourier Transform ◽  
The Impact ◽  
Resonance Broadening

Theoretical expressions are derived for the complete line shape in resonance broadening using two independent methods, viz. (a) propagator techniques, (b) kinetic theory techniques. These expressions are valid for any duration of collision in the binary collision regime, and reduce to the impact (static) limit results when the average duration of collision is small (large). The expressions involve the Fourier transform of the two body collision operator and, therefore, these are quite suitable for actual numerical calculations.

scholarly journals Hydrogen Stark Broadened Brackett lines

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
C. Stehlé ◽  
S. Fouquet
Keyword(s):  
Line Shape ◽  
High Density ◽  
Stellar Atmospheres ◽  
Low Density ◽  
Dynamic Effects ◽  
Circumstellar Envelopes ◽  
Static Limit ◽  
Line Core ◽  
The Impact

Stark-broadened lines of the hydrogen Brackett series are computed for the conditions of stellar atmospheres and circumstellar envelopes. The computation is performed within the Model Microfield Method, which includes the ion dynamic effects and makes the bridge between the impact limit at low density and the static limit at high density and in the line wings. The computation gives the area normalized line shape, from the line core up to the static line wings.

Complete Line Shape for the Impact, Static, and the Intermediate Regions

1975 ◽  
Vol 53 (1) ◽  
pp. 84-92 ◽  
Author(s):  
R. P. Srivastava ◽  
H. R. Zaidi
Keyword(s):  
Density Dependence ◽  
Line Width ◽  
Line Shape ◽  
Translational Motion ◽  
Excited Level ◽  
Dipole Interaction ◽  
Line Shapes ◽  
Classical Path ◽  
The Impact ◽  
Resonance Broadening

Line shapes are calculated for the resonance broadening of an excited level through the dipole–dipole interaction. The calculations are based on two main approximations: (1) two body collisions and (2) straight classical path for the translational motion. The results are valid over the complete region extending from the impact to the static regimes. It is shown that, under suitable conditions, the incomplete collisions can give rise to (a) a splitting of the line at the center and (b) nonlinear density dependence of the line width.

scholarly journals Pitfalls in the Evaluation of X-ray Diffraction Line Shape

1988 ◽  
Vol 41 (2) ◽  
pp. 237 ◽  
Author(s):  
Gerhard Zorn
Keyword(s):  
Fourier Transform ◽  
Computer Simulations ◽  
Line Shape ◽  
Fourier Transformation ◽  
Step Width ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sampling Points ◽  
The Fourier Transform ◽  
Reliable Basis

The sources of errors in the analysis of X-ray diffraction profiles are described, and recipes are given to minimise or eliminate these errors. It is proposed that a sample at high temperatures is used as a standard. The influence of measurement statistics on the Fourier transform of deconvoluted functions is demonstrated through computer simulations. The necessity for smoothing procedures is stressed. It is shown how the parameter step width, number of sampling points, and position of origin for the Fourier transformation can be optimised, and thus a reliable basis can be created for the interpretation of the Fourier transform in terms of crystallite size, size distribution, and micros train.

scholarly journals Analysis of Satellite Compass Error’s Spectrum

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4067
Author(s):  
Andrzej Felski ◽  
Krzysztof Jaskólski ◽  
Karolina Zwolak ◽  
Paweł Piskur
Keyword(s):  
Fourier Transform ◽  
Frequency Spectrum ◽  
Fiber Optic ◽  
Steering System ◽  
International Convention ◽  
Standard Data ◽  
Fishing Vessels ◽  
Straight Line ◽  
The Fourier Transform ◽  
The Impact

The satellite compass is one of new variants of satellite navigational devices. Is it still treated with caution on International Convention for the Safety of Life at Sea (SOLAS) vessels, but has become popular on the fishing vessels and pleasure crafts. The standard data obtained by such devices suggest accuracy of satellite compasses at a level of about 1 degree, so it seems to be as accurate as gyro or the magnetic equivalent. A changeability of heading errors, especially its frequency spectrum, is analyzed and presented in the paper. The results of comparison of an onboard standard gyrocompass, a fiber-optic gyrocompass (FOG) and a satellite compass in real shipping circumstances have been discussed based on the available literature and previous research. The similar comportment of these compasses are confirmed, however, in real circumstances it is difficult to separate heading oscillations produced by the ships yaw (or helmsman abilities) from the oscillations of the compass. Analysis of the heading oscillations has been performed based on the measurements of the heading indications of stationary compass devices and the devices mounted on the vehicles moving on the straight line (straight part of a road and tram line) to separate the impact of the vessel steering system. Results of heading changeability in the frequency domain are presented based on the Fourier transform theory.

scholarly journals Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

2021 ◽  
Vol 11 (6) ◽  
pp. 2582
Author(s):  
Lucas M. Martinho ◽  
Alan C. Kubrusly ◽  
Nicolás Pérez ◽  
Jean Pierre von der Weid
Keyword(s):  
Fourier Transform ◽  
Guided Waves ◽  
Strain Level ◽  
Energy Concentration ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
The Fourier Transform ◽  
Short Time ◽  
Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

Determination of starch crystallinity with the Fourier-transform terahertz spectrometer

2021 ◽  
Vol 262 ◽  
pp. 117928
Author(s):  
Shusaku Nakajima ◽  
Shuhei Horiuchi ◽  
Akifumi Ikehata ◽  
Yuichi Ogawa
Keyword(s):  
Fourier Transform ◽  
The Fourier Transform ◽  
Starch Crystallinity
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