scholarly journals The Frequency Fluctuation Model for the van der Waals Broadening

2021 ◽  
Author(s):  
Andrei Letunov ◽  
Valery Lisitsa ◽  
Valery Astapenko
Keyword(s):  
Experimental Data ◽  
Spectral Line ◽  
Line Shape ◽  
Frequency Fluctuation ◽  
Neutral Particles ◽  
Line Shapes ◽  
First Time ◽  
Analytical Expressions ◽  
Fluctuation Model ◽  
Good Agreement

The effect of atomic and molecular microfied dynamics on spectral line shapes is under consideration. This problem is treated in the framework of the Frequency Fluctuation Model (FFM). For the first time the FFM is tested for the broadening of a spectral line by neutral particles. The usage of the FFM allows one to derive simple analytical expressions and perform fast calculations of the intensity profile. The obtained results was compared with Chen and Takeo theory (CT), which is in a good agreement with experimental data. It was demonstrated that for moderate values of temperature and density the FFM successfully describes the effect of the microfield dynamics on a spectral line shape.

Improved Frequency Fluctuation Model for Spectral Line Shape Calculations in Fusion Plasmas

2010 ◽  
Author(s):  
S. Ferri ◽  
A. Calisti ◽  
C. Mossé ◽  
B. Talin ◽  
V. Lisitsa ◽  
...  
Keyword(s):  
Spectral Line ◽  
Line Shape ◽  
Frequency Fluctuation ◽  
Fusion Plasmas ◽  
Spectral Line Shape ◽  
Fluctuation Model

Frequency-fluctuation model applied to Stark-Zeeman spectral line shapes in plasmas

2011 ◽  
Vol 84 (2) ◽  
Author(s):  
S. Ferri ◽  
A. Calisti ◽  
C. Mossé ◽  
L. Mouret ◽  
B. Talin ◽  
...  
Keyword(s):  
Spectral Line ◽  
Frequency Fluctuation ◽  
Line Shapes ◽  
Fluctuation Model

Dose-window dependence on Si crystal orientation in separation by implanted oxygen substrate formation

2004 ◽  
Vol 19 (12) ◽  
pp. 3607-3613 ◽  
Author(s):  
H. Iikawa ◽  
M. Nakao ◽  
K. Izumi
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Crystal Orientation ◽  
Oxygen Ion ◽  
The Difference ◽  
First Time ◽  
Good Agreement

Separation by implemented oxygen (SIMOX)(111) substrates have been formed by oxygen-ion (16O+) implantation into Si(111), showing that a so-called “dose-window” at 16O+-implantation into Si differs from Si(100) to Si(111). In SIMOX(100), an oxygen dose of 4 × 1017/cm2 into Si(100) is widely recognized as the dose-window when the acceleration energy is 180 keV. For the first time, our work shows that an oxygen dose of 5 × 1017/cm2 into Si(111) is the dose-window for the formation of SIMOX(111) substrates when the acceleration energy is 180 keV. The difference between dose-windows is caused by anisotropy of the crystal orientation during growth of the faceted buried SiO2. We also numerically analyzed the data at different oxidation velocities for each facet of the polyhedral SiO2 islands. Numerical analysis results show good agreement with the experimental data.

The impact theory of spectral line shapes: a paradigm shift

2013 ◽  
Vol 91 (11) ◽  
pp. 879-895 ◽  
Author(s):  
A.D. May ◽  
W.-K. Liu ◽  
F.R.W. McCourt ◽  
R. Ciuryło ◽  
J. Sanchez-Fortún Stoker ◽  
...  
Keyword(s):  
Spectral Line ◽  
Line Shape ◽  
Paradigm Shift ◽  
Wigner Distribution ◽  
Kinetic Equations ◽  
Line Profiles ◽  
Line Shapes ◽  
Experimental Line ◽  
Impact Theory ◽  
The Impact

An overview of the binary collision impact theory of spectral line shapes has been given to provide a unified statistical mechanical approach to line-shape theory, laser theory, nonlinear optics, and transport phenomena in dilute gases. The computation of spectral line profiles corresponding to those obtained from ultra-high-resolution spectral line-shape measurements requires numerical ab initio calculation of scattering amplitudes directly from the underlying dynamics of collisions between radiatively active molecules and their perturbers. The Wigner distribution function–density matrix is utilized to describe the kinetic theory of spectral line shapes and to discuss the various collisional processes that contribute to the kernel of kinetic equations. The influence of features of the potential energy surface on spectral parameters is also discussed, and the importance of comparing experimental line profiles directly with numerically computed line shapes obtained from reliable interaction potentials is emphasized. This contrasts sharply with the universal practice of comparing experimental line widths and shifts using some average or approximate theoretical scattering cross-sections and it contrasts sharply with fitting experimental profiles to some convenient analytical line-shape model; hence the phrase “a paradigm shift” in the title of this work.

Reflectivity of 1D photonic crystals: A comparison of computational schemes with experimental results

2018 ◽  
Vol 32 (11) ◽  
pp. 1850136 ◽  
Author(s):  
J. S. Pérez-Huerta ◽  
D. Ariza-Flores ◽  
R. Castro-García ◽  
W. L. Mochán ◽  
G. P. Ortiz ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Photonic Crystals ◽  
Spectral Line ◽  
Multilayer Structures ◽  
One Dimensional ◽  
Line Shapes ◽  
Number Of Layers ◽  
Reflectivity Spectra ◽  
Bloch Modes ◽  
Good Agreement

We report the reflectivity of one-dimensional finite and semi-infinite photonic crystals, computed through the coupling to Bloch modes (BM) and through a transfer matrix method (TMM), and their comparison to the experimental spectral line shapes of porous silicon (PS) multilayer structures. Both methods reproduce a forbidden photonic bandgap (PBG), but slowly-converging oscillations are observed in the TMM as the number of layers increases to infinity, while a smooth converged behavior is presented with BM. The experimental reflectivity spectra is in good agreement with the TMM results for multilayer structures with a small number of periods. However, for structures with large amount of periods, the measured spectral line shapes exhibit better agreement with the smooth behavior predicted by BM.

Powder Zeeman NQR Study on 123Sb in Sb(C6H5)3

2002 ◽  
Vol 57 (6-7) ◽  
pp. 304-306
Author(s):  
O. Ege ◽  
S. Maekawa ◽  
H. Negita
Keyword(s):  
Computer Simulation ◽  
Line Shape ◽  
Asymmetry Parameter ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Line Shapes ◽  
Quadrupole Coupling ◽  
Saddle Type ◽  
Lower Series ◽  
Good Agreement

Powder Zeeman NQR spectra of 123Sb in Sb(C6H5)3 were studied by means of a computer simulation and an experiment. The 123Sb nucleus has spin 7/2. There are two non-equivalent 123Sb atoms in the crystal of Sb(C6H5)3, so that there are two series of three transition lines (higher series: ν1h, ν2h, ν3h; lower series: ν11, ν21, v31). The powder Zeeman spectra for ν1h, based on the transition between the levels mI = ±1/2 and ±3/2, were observed at 77 K under the two conditions that i) the oscillation coil and the static magnetic coil were set coaxially and parallel, and ii) they were set perpendicular to each other. The powder line shapes for ν1h, which is the lowest line of the higher series due to 123Sb nuclei, were in good agreement with those from a computer simulation under the conditions i) and ii), showing that the asymmetry parameter of the field gradient is very small (η = 0). The line shape from i) exhibits two shoulders (saddle type), as it appeared for nuclear spin 5/2 and η = 0. The quadrupole coupling constant for 1h, calculated from the resonance frequency 47.820 MHz and the observed η, is 669.480 MHz at 77 K.

Broadening and shifting of the Raman Q branch in D2 and D2–He mixtures, II: line shapes, fitting routines, and effects nonlinear in density

1994 ◽  
Vol 72 (11-12) ◽  
pp. 891-896 ◽  
Author(s):  
P. M. Sinclair ◽  
P. Duggan ◽  
J. W. Forsman ◽  
J. R. Drummond ◽  
A. D. May
Keyword(s):  
Molecular Dynamics ◽  
Line Shape ◽  
Preceding Paper ◽  
Binary Collision ◽  
Spectral Profile ◽  
Lorentzian Line ◽  
Line Shapes ◽  
And Shifts ◽  
Three Body ◽  
First Time

In the preceding paper we fitted the experimental profiles using a single Lorentzian line shape and assumed that the width and shift were proportional to the density. Here we discuss nonlinear contributions to widths and shifts and present a different spectral profile and analysis that allows us (i) to determine unbiased, binary collision, impact limit, broadening and shifting coefficients; (ii) to disentangle several effects nonlinear in the density; and, subsequently, (iii) to observe broadening and shifting arising purely from the correlation between perturbers and three-body interactions. This is a new avenue of research in molecular dynamics. In addition, measurements of the broadening of the depolarized part of the Q branch in D2 are reported for the first time.

Collisional Narrowing and the Foreign Gas Broadening of Spectral Line Shapes

1972 ◽  
Vol 50 (22) ◽  
pp. 2792-2800 ◽  
Author(s):  
H. R. Zaidi
Keyword(s):  
Spectral Line ◽  
Line Shape ◽  
Point Of View ◽  
Many Body ◽  
Spectral Line Shape ◽  
Many Body Theory ◽  
Line Shapes ◽  
The Many ◽  
The Impact ◽  
Body Theory

The problem of collisional narrowing and broadening of spectral line shape in a gas is considered from the point of view of propagator technique of the many body theory. The case in which the radiator and perturbers are of different species is considered in this paper. In the impact limit, the propagator equations reduce to a form which is a generalization of the classical equations used in the previous theories. The line shapes resulting from the two approaches are compared and possible generalizations are discussed.

LOW TEMPERATURE SPECIFIC HEAT OF (KBr)1-x(KCN)x MIXED CRYSTAL

2003 ◽  
Vol 17 (26) ◽  
pp. 1391-1398 ◽  
Author(s):  
N. K. GAUR ◽  
NUPINDER KAUR ◽  
MANIK MANAKE ◽  
JYOTSNA GALGALE ◽  
R. K. SINGH
Keyword(s):  
Experimental Data ◽  
Thermal Properties ◽  
Specific Heat ◽  
Mixed Crystal ◽  
Body Force ◽  
Molecular Force ◽  
Low Temperature Specific Heat ◽  
Three Body ◽  
First Time ◽  
Good Agreement

We have investigated the cohesive and thermodynamic properties of ( KBr )1-x( KCN )x using an extended three-body force shell model (ETSM), which has been found to be adequately suitable for the description of orientationally disordered mixed cyanide-halide crystals. The specific heat of ( KBr )1-x( KCN )x for compositions (x=0.53, 0.65, 0.73, 0.84 and 0.93) at temperature 10 K ≤T≤150 K have been computed using the ETSM for the first time. The paper also reports the calculated results on Debye temperature (Θ D ), cohesive energy (Φ), compressibility (β), molecular force constant (f) and Restrahlen frequency (ν0) of ( KBr )1-x( KCN )x. The results on specific heat and some other thermal properties are in good agreement with their available experimental data.

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