Modeling the spectral line shapes with speed-dependent broadening and Dicke narrowing

2001 ◽  
Vol 79 (10) ◽  
pp. 1209-1222 ◽  
Author(s):  
D A Shapiro ◽  
R Ciurylo ◽  
R Jaworski ◽  
A D May
Keyword(s):  
Relative Size ◽  
Spectral Lines ◽  
Three Dimension ◽  
Relaxation Equation ◽  
Opposite Case ◽  
Collisional Broadening ◽  
Line Shapes ◽  
Impact Approximation ◽  
Speed Dependence ◽  
The Impact

Shapes of pressure- and Doppler-broadened spectral lines are obtained by solving exactly a three-dimension transport and (or) relaxation equation. The speed dependence of collisional broadening and shifting caused by dephasing collisions and Dicke narrowing caused by velocity-changing collisions are taken into account within the impact approximation. The Rautian–Sobelman and Keilson–Storer models are used to describe velocity-changing collisions. We show in the high density or hydrodynamic limit that both models lead to a profile that is the weighted sum of Lorentz profiles if the collisional broadening is much greater than the frequency of velocity-changing collisions and to the ordinary Lorentz profile in the opposite case. This shows that the relative size of the optical and kinetic cross section is important in determining the shape of absorption curves. The analytical solutions may be useful in modeling absorption profiles for remote sensing of the atmosphere. PACS No.: 32.70Jz

scholarly journals From the Vector to Scalar Perturbations Addition in the Stark Broadening Theory of Spectral Lines

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 176
Author(s):  
Valery Astapenko ◽  
Andrei Letunov ◽  
Valery Lisitsa
Keyword(s):  
Spectral Line ◽  
Stark Effect ◽  
Coulomb Field ◽  
Spectral Lines ◽  
Alternative Methods ◽  
Scalar Perturbation ◽  
Numerical Comparison ◽  
Line Shapes ◽  
Stark Effects ◽  
The Impact

The effect of plasma Coulomb microfied dynamics on spectral line shapes is under consideration. The analytical solution of the problem is unachievable with famous Chandrasekhar–Von-Neumann results up to the present time. The alternative methods are connected with modeling of a real ion Coulomb field dynamics by approximate models. One of the most accurate theories of ions dynamics effect on line shapes in plasmas is the Frequency Fluctuation Model (FFM) tested by the comparison with plasma microfield numerical simulations. The goal of the present paper is to make a detailed comparison of the FFM results with analytical ones for the linear and quadratic Stark effects in different limiting cases. The main problem is connected with perturbation additions laws known to be vector for small particle velocities (static line shapes) and scalar for large velocities (the impact limit). The general solutions for line shapes known in the frame of scalar perturbation additions are used to test the FFM procedure. The difference between “scalar” and “vector” models is demonstrated both for linear and quadratic Stark effects. It is shown that correct transition from static to impact limits for linear Stark-effect needs in account of the dependence of electric field jumping frequency in FFM on the field strengths. However, the constant jumping frequency is quite satisfactory for description of the quadratic Stark-effect. The detailed numerical comparison for spectral line shapes in the frame of both scalar and vector perturbation additions with and without jumping frequency field dependence for the linear and quadratic Stark effects is presented.

AGN evolution as seen in spectral lines: The case of narrow-line Seyfert 1s

2019 ◽  
Vol 15 (S356) ◽  
pp. 94-94
Author(s):  
Marco Berton
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spectroscopic Studies ◽  
Spectral Lines ◽  
Narrow Line ◽  
Line Profiles ◽  
Line Shapes ◽  
Fundamental Information ◽  
Line Region ◽  
Gaussian Samples

AbstractLine profiles can provide fundamental information on the physics of active galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s) this is of particular importance since past studies revealed how their permitted line profiles are well reproduced by a Lorentzian function instead of a Gaussian. This has been explained with different properties of the broad-line region (BLR), which may present more pronounced turbulent motions in NLS1s with respect to other AGN. We investigated the line profiles in a recent large NLS1 sample classified using SDSS, and we divided the sources into two subsamples according to their line shapes, Gaussian or Lorentzian. The line profiles seem to separate all the properties of NLS1s. Black hole mass, Eddington ratio, [OIII] luminosity, and Fe II strength are all very different in the Lorentzian and Gaussian samples, as well as their position on the quasar main sequence. We interpret this in terms of evolution within the class of NLS1s. The Lorentzian sources may be the youngest objects, while Gaussian profiles may be typically associated to more evolved objects. Further detailed spectroscopic studies are needed to fully confirm our hypothesis.

R&D Heterogeneity and the Impact of R&D Subsidies*

2021 ◽  
Author(s):  
Sigurd M⊘lster Galaasen ◽  
Alfonso Irarrazabal
Keyword(s):  
Economic Impact ◽  
Growth Model ◽  
Relative Size ◽  
Schumpeterian Growth ◽  
Size Dependent ◽  
Investment Growth ◽  
The Impact ◽  
D Investment ◽  
Model Fits

Abstract This paper studies the determinants of R&D heterogeneity and the economic impact of R&D subsidies. We estimate a Schumpeterian growth model featuring firms with heterogeneous innovation efficiencies. The model fits well the R&D investment distribution, and the frequency and relative size of R&D performers. Using the model we study the impact of a Norwegian R&D reform targeting firms with R&D spending below a certain threshold. The size-dependent subsidy increases aggregate R&D investment by 11.7%, but reduces growth and welfare. In contrast, a uniform subsidy stimulates investment, growth and welfare.

scholarly journals Templated quasicrystalline ordering of single elements and molecules

2014 ◽  
Vol 70 (a1) ◽  
pp. C81-C81
Author(s):  
H. R. Sharma ◽  
J. A. Smerdon ◽  
K. Nozawa ◽  
K. M. Young ◽  
T. P. Yadav ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Chemical Properties ◽  
Scanning Tunneling ◽  
Three Dimension ◽  
Tunneling Microscopy ◽  
Quantum Size ◽  
Adsorption Energies ◽  
Molecular Layers ◽  
Physical And Chemical ◽  
The Impact

We have used quasicrystals as templates for the exploration of new epitaxial phenomena. Several interesting results have been observed in the growth on surfaces of the common Al-based quasicrystals [1]. These include pseudomorphic monolayers, quasiperiodically modulated multilayer structures, and fivefold-twinned islands with magic heights influenced by quantum size effects [1]. Here we present our recent works on the growth of various elements and molecules on a new substrate, icosahedral (i) Ag-In-Yb quasicrystal, which have resulted in various epitaxial phenomena not observed previously. The growth of Pb on the five-fold surface of i-Ag-In-Yb yields a film which possesses quasicrystalline ordering in three-dimension [2]. Using scanning tunneling microscopy (STM) and DFT calculations of adsorption energies, we find that lead atoms occupy the positions of atoms in the rhombic triacontahedral (RTH) cluster, the building block of the substrate, and thus grow in layers with different heights and adsorption energies. The adlayer–adlayer interaction is crucial for stabilizing the epitaxial quasicrystalline structure. We will also present the first example of quasicrystalline molecular layers. Pentacene adsorbs at tenfold-symmetric sites of Yb atoms around surface-bisected RTH clusters, yielding quasicrystalline order [3]. Similarly, C-60 growth on the five-fold surface of i-Al-Cu-Fe at elevated temperature produces quasicrystalline layer, where the growth is mediated by Fe atoms on the substrate surface [3]. The finding of quasicrystalline thin films of single elements and molecules opens an avenue for further investigation of the impact of the aperiodic atomic order over periodic order on the physical and chemical properties of materials.

Energy or carbon? Exploring the relative size of universal zero carbon and zero energy design spaces

2018 ◽  
Vol 40 (3) ◽  
pp. 319-339 ◽  
Author(s):  
Anna Parkin ◽  
Manuel Herrera ◽  
David A Coley
Keyword(s):  
Design Space ◽  
Relative Size ◽  
Building Design ◽  
Zero Energy ◽  
Software Environment ◽  
Space Forms ◽  
Regulatory Frameworks ◽  
Regulatory Standards ◽  
Zero Carbon ◽  
The Impact

One aim of zero carbon, or zero energy, buildings is to help slow climate change. However, regulatory definitions frequently miss substantial emissions, for example ones associated with the materials the building is constructed from, thereby compromising this goal. Unfortunately, including such emissions might restrict the design space, reduce architectural freedom or greatly increase costs. This work presents a new framework for examining the problem. The zero carbon/energy design and regulatory space forms a sub-space of the hyper-volume enclosing all possible designs and regulatory frameworks. A new mathematical/software environment was developed which allows the size and shape of this sub-space to be investigated for the first time. Twenty-four million building design/regulatory standard combinations were modelled and assessed using a tree classification approach. It was found that a worldwide zero standard that includes embodied emissions is possible and is easier to achieve if a carbon rather than an energy metric is adopted, with the design space twice the size for a carbon metric. This result is important for the development of more encompassing regulations, and the novel methods developed applicable to other aspects of construction controlled by regulation where there is the desire to examine the impact of new regulations prior to legislation. Practical application: As energy standards become more strict, and given the growth in non-regulatory standards (such as Passivhaus), there is the need to study the potential impact of any element of a standard on the range of designs that can be built or the materials that can be used. This work sets out a general framework and method for doing this. The approach and results will be of interest to policy makers, but also to engineers and architects wondering what the key constraints to design the adoption of various philosophies to low energy/carbon standards might have within their work. For example, the implications of the building standard (or client) requiring embodied emissions to be included or the energy balance period for renewable generation to be monthly, not annual.

The characteristic spectral lines of target atoms in the impact of40Ar q+ ions on metal surfaces

2004 ◽  
Vol 47 (6) ◽  
pp. 729-736
Author(s):  
Xiao’an Zhang ◽  
Yongtao Zhao ◽  
Fuli Li ◽  
Zhihu Yang ◽  
Guoqing Xiao ◽  
...  
Keyword(s):  
Metal Surfaces ◽  
Spectral Lines ◽  
The Impact

Measurement of Dysprosium Stark Width and the Electron Impact Width Parameter

2018 ◽  
Vol 73 (2) ◽  
pp. 203-213 ◽  
Author(s):  
Jhonatha R. dos Santos ◽  
Jonas Jakutis Neto ◽  
N. Rodrigues ◽  
M.G. Destro ◽  
José W. Neri ◽  
...  
Keyword(s):  
Electron Density ◽  
Impact Parameter ◽  
Plasma Temperature ◽  
Spectral Lines ◽  
Emission Lines ◽  
Spectroscopic Methods ◽  
Species Concentration ◽  
The Impact ◽  
Stark Width

In this work, we suggest a methodology to determine the impact parameter for neutral dysprosium emission lines from the characterization of the plasma generated by laser ablation in a sealed chamber filled with argon. The procedure is a combination of known consistent spectroscopic methods for plasma temperature determination, electron density, and species concentration. With an electron density of 3.1 × 1018 cm–3 and temperature close to 104 K, we estimated the impact electron parameter for nine spectral lines of the neutral dysprosium atom. The gaps in the impact parameter data in the literature, mainly for heavy elements, stress the importance of the proposed method.

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