The Experts below are selected from a list of 681852 Experts worldwide ranked by ideXlab platform
N Konjevic - One of the best experts on this subject based on the ideXlab platform.
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stark width and shift for electron Number Density diagnostics of low temperature plasma application to silicon laser induced breakdown spectroscopy
Spectrochimica Acta Part B: Atomic Spectroscopy, 2017Co-Authors: M Ivkovic, N KonjevicAbstract:Abstract In this work we summarize, analyze and critically evaluate experimental procedures and results of LIBS electron Number Density plasma characterization using as examples Stark broadened Si I and Si II line profiles. Selected publications are covering the time period from very beginning of silicon LIBS studies until the end of the year 2015. To perform the analysis of experimental LIBS data, the testing of available semiclassical theoretical Stark broadening parameters for Si I and Si II lines was accomplished first. This is followed by the description of experimental setups, results and details of experimental procedure relevant for the line shape analysis of spectral lines used for plasma characterization. Although most of results and conclusions of this analysis are related to the application of silicon lines for LIBS characterization they are of general importance and may be applied to other elements and different low-temperature plasma sources. The analysis of experimental procedures used for LIBS diagnostics from emission profiles of non-hydrogenic spectral lines is carried out in the following order: the influence of laser ablation and crater formation, spatial and temporal plasma observation, line self-absorption and experimental profile deconvolution, the contribution of ion broadening in comparison with electron impacts contributions to the line width in case of neutral atom line and some other aspects of line shape analysis are considered. The application of Stark shift for LIBS diagnostics is demonstrated and discussed. Finally, the recommendations for an improvement of experimental procedures for LIBS electron Number Density plasma characterization are offered.
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hydrogen balmer lines for low electron Number Density plasma diagnostics
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: N Konjevic, M Ivkovic, N M SakanAbstract:Abstract We present an analysis of the procedure for plasma electron Number Density, N e , diagnostics based on the comparison of theoretical and experimental shape or width of hydrogen Balmer lines. Low N e diagnostics, requiring an extension of available theoretical Stark broadening data tables was examined first. The difficulties encountered during experimental line profile analysis at low N e are discussed and appropriate procedures suggested. The widely adopted deconvolution of experimental profile by fitting with a Voigt function is examined and it is shown that this deconvolution introduces large systematic error in Stark width determination. This uncertainty can be decreased but never completely avoided by fixing the Gaussian part of the Voigt function. Simple formulas of satisfactory accuracy for deconvolution at the half width of experimental profile were investigated and their application recommended. The contribution of Van der Waals broadening to the experimental profile is examined and the correction for its contribution discussed. Approximate and reliable formulas for the evaluation of N e from the Stark width were critically evaluated. To estimate the applicability of different sets of theoretical data for N e diagnostics, a comparison of theory versus experiments was carried out and best data tables were recommended. For low N e diagnostics the application of higher members of Balmer series is advised whenever possible.
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a simple line shape technique for electron Number Density diagnostics of helium and helium seeded plasmas
Spectrochimica Acta Part B: Atomic Spectroscopy, 2010Co-Authors: M Ivkovic, Manuel A Gonzalez, S Jovicevic, M A Gigosos, N KonjevicAbstract:Abstract The results of an experimental study of the He I 447.1 nm line and its forbidden component at high electron Number Density are presented and compared with profiles calculated using computer simulation method. Michelson interferometer at 632.8 nm was used to measure plasma electron Number Density in the range (1–7) × 10 23 m − 3 while electron temperatures for the same experimental conditions in the range of 25 000 K to 35 000 K were determined using several spectroscopic techniques. The agreement of experimental overall line shape with computer simulation results is within 10% of what is well within theoretical and experimental uncertainty. This favorable comparison enabled the development of a simple approximate formula for the evaluation of electron Number Density from the measurement of wavelength separation between peaks of allowed and forbidden lines. This technique of plasma diagnostics is not sensitive to the presence of self-absorption of strong He I allowed line. The derivation of approximate formula with estimated accuracy of 15% was followed by detailed comparison with other experimental and theoretical data.
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a program for the evaluation of electron Number Density from experimental hydrogen balmer beta line profiles
Spectrochimica Acta Part B: Atomic Spectroscopy, 2002Co-Authors: R žikic, Manuel A Gonzalez, M Ivkovic, M A Gigosos, N KonjevicAbstract:Abstract A program for the determination of plasma electron Number Density, 1020≤(Ne)≤1023 m−3, from the comparison of experimental and theoretical hydrogen Balmer beta (Hβ) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a user's choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for Ne determination. The Hβ asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles.
M Ivkovic - One of the best experts on this subject based on the ideXlab platform.
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stark width and shift for electron Number Density diagnostics of low temperature plasma application to silicon laser induced breakdown spectroscopy
Spectrochimica Acta Part B: Atomic Spectroscopy, 2017Co-Authors: M Ivkovic, N KonjevicAbstract:Abstract In this work we summarize, analyze and critically evaluate experimental procedures and results of LIBS electron Number Density plasma characterization using as examples Stark broadened Si I and Si II line profiles. Selected publications are covering the time period from very beginning of silicon LIBS studies until the end of the year 2015. To perform the analysis of experimental LIBS data, the testing of available semiclassical theoretical Stark broadening parameters for Si I and Si II lines was accomplished first. This is followed by the description of experimental setups, results and details of experimental procedure relevant for the line shape analysis of spectral lines used for plasma characterization. Although most of results and conclusions of this analysis are related to the application of silicon lines for LIBS characterization they are of general importance and may be applied to other elements and different low-temperature plasma sources. The analysis of experimental procedures used for LIBS diagnostics from emission profiles of non-hydrogenic spectral lines is carried out in the following order: the influence of laser ablation and crater formation, spatial and temporal plasma observation, line self-absorption and experimental profile deconvolution, the contribution of ion broadening in comparison with electron impacts contributions to the line width in case of neutral atom line and some other aspects of line shape analysis are considered. The application of Stark shift for LIBS diagnostics is demonstrated and discussed. Finally, the recommendations for an improvement of experimental procedures for LIBS electron Number Density plasma characterization are offered.
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hydrogen balmer lines for low electron Number Density plasma diagnostics
Spectrochimica Acta Part B: Atomic Spectroscopy, 2012Co-Authors: N Konjevic, M Ivkovic, N M SakanAbstract:Abstract We present an analysis of the procedure for plasma electron Number Density, N e , diagnostics based on the comparison of theoretical and experimental shape or width of hydrogen Balmer lines. Low N e diagnostics, requiring an extension of available theoretical Stark broadening data tables was examined first. The difficulties encountered during experimental line profile analysis at low N e are discussed and appropriate procedures suggested. The widely adopted deconvolution of experimental profile by fitting with a Voigt function is examined and it is shown that this deconvolution introduces large systematic error in Stark width determination. This uncertainty can be decreased but never completely avoided by fixing the Gaussian part of the Voigt function. Simple formulas of satisfactory accuracy for deconvolution at the half width of experimental profile were investigated and their application recommended. The contribution of Van der Waals broadening to the experimental profile is examined and the correction for its contribution discussed. Approximate and reliable formulas for the evaluation of N e from the Stark width were critically evaluated. To estimate the applicability of different sets of theoretical data for N e diagnostics, a comparison of theory versus experiments was carried out and best data tables were recommended. For low N e diagnostics the application of higher members of Balmer series is advised whenever possible.
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a simple line shape technique for electron Number Density diagnostics of helium and helium seeded plasmas
Spectrochimica Acta Part B: Atomic Spectroscopy, 2010Co-Authors: M Ivkovic, Manuel A Gonzalez, S Jovicevic, M A Gigosos, N KonjevicAbstract:Abstract The results of an experimental study of the He I 447.1 nm line and its forbidden component at high electron Number Density are presented and compared with profiles calculated using computer simulation method. Michelson interferometer at 632.8 nm was used to measure plasma electron Number Density in the range (1–7) × 10 23 m − 3 while electron temperatures for the same experimental conditions in the range of 25 000 K to 35 000 K were determined using several spectroscopic techniques. The agreement of experimental overall line shape with computer simulation results is within 10% of what is well within theoretical and experimental uncertainty. This favorable comparison enabled the development of a simple approximate formula for the evaluation of electron Number Density from the measurement of wavelength separation between peaks of allowed and forbidden lines. This technique of plasma diagnostics is not sensitive to the presence of self-absorption of strong He I allowed line. The derivation of approximate formula with estimated accuracy of 15% was followed by detailed comparison with other experimental and theoretical data.
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a program for the evaluation of electron Number Density from experimental hydrogen balmer beta line profiles
Spectrochimica Acta Part B: Atomic Spectroscopy, 2002Co-Authors: R žikic, Manuel A Gonzalez, M Ivkovic, M A Gigosos, N KonjevicAbstract:Abstract A program for the determination of plasma electron Number Density, 1020≤(Ne)≤1023 m−3, from the comparison of experimental and theoretical hydrogen Balmer beta (Hβ) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a user's choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for Ne determination. The Hβ asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles.
Ho Seong Hwang - One of the best experts on this subject based on the ideXlab platform.
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quiescent compact galaxies at intermediate redshift in the cosmos field the Number Density
The Astrophysical Journal, 2015Co-Authors: Ivana Damjanov, Margaret J Geller, Jabran H Zahid, Ho Seong HwangAbstract:We investigate the evolution of compact galaxy Number Density over the redshift range . Our sample consists of galaxies with secure spectroscopic redshifts observed in the COSMOS field. With the large uncertainties, the compact galaxy Number Density trend with redshift is consistent with a constant value over the interval . Our Number Density estimates are similar to the estimates at for equivalently selected compact samples. Small variations in the abundance of the COSMOS compact sources as a function of redshift correspond to known structures in the field. The constancy of the compact galaxy Number Density is robust and insensitive to the compactness threshold or the stellar mass range (for ). To maintain constant Number Density any size growth of high-redshift compact systems with decreasing redshift must be balanced by a formation of quiescent compact systems at .
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quiescent compact galaxies at intermediate redshift in the cosmos field the Number Density
arXiv: Astrophysics of Galaxies, 2015Co-Authors: Ivana Damjanov, Margaret J Geller, Jabran H Zahid, Ho Seong HwangAbstract:We investigate the evolution of compact galaxy Number Density over the redshift range $0.2 1$ for equivalently selected compact samples. Small variations in the abundance of the COSMOS compact sources as a function of redshift correspond to known structures in the field. The constancy of the compact galaxy Number Density is robust and insensitive to the compactness threshold or the stellar mass range (for $M_\ast>10^{10}\, M_\odot$). To maintain constant Number Density any size growth of high-redshift compact systems with decreasing redshift must be balanced by formation of quiescent compact systems at $z<1$.
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the Number Density of quiescent compact galaxies at intermediate redshift
The Astrophysical Journal, 2014Co-Authors: Ivana Damjanov, Margaret J Geller, Ho Seong Hwang, Igor ChilingarianAbstract:Massive compact systems at 0.2 < z < 0.6 are the missing link between the predominantly compact population of massive quiescent galaxies at high redshift and their analogs and relics in the local volume. The evolution in Number Density of these extreme objects over cosmic time is the crucial constraining factor for the models of massive galaxy assembly. We select a large sample of ~200 intermediate-redshift massive compacts from the Baryon Oscillation Spectroscopic Survey (BOSS) spectroscopy by identifying point-like Sloan Digital Sky Survey photometric sources with spectroscopic signatures of evolved redshifted galaxies. A subset of our targets have publicly available high-resolution ground-based images that we use to augment the dynamical and stellar population properties of these systems by their structural parameters. We confirm that all BOSS compact candidates are as compact as their high-redshift massive counterparts and less than half the size of similarly massive systems at z ~ 0. We use the completeness-corrected Numbers of BOSS compacts to compute lower limits on their Number densities in narrow redshift bins spanning the range of our sample. The abundance of extremely dense quiescent galaxies at 0.2 < z < 0.6 is in excellent agreement with the Number densities of these systems at high redshift. Our lower limits support the models of massive galaxy assembly through a series of minor mergers over the redshift range 0 < z < 2.
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the Number Density of quiescent compact galaxies at intermediate redshift
arXiv: Astrophysics of Galaxies, 2014Co-Authors: Ivana Damjanov, Margaret J Geller, Ho Seong Hwang, Igor ChilingarianAbstract:Massive compact systems at 0.2
Benjamin Joachimi - One of the best experts on this subject based on the ideXlab platform.
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simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy Number Density correlations
Astronomy and Astrophysics, 2010Co-Authors: Benjamin Joachimi, S L BridleAbstract:Aims. Cosmic shear is a powerful method to constrain cosmology, provided that any systematic effects are under control. The intrinsic alignment of galaxies is expected to severely bias parameter estimates if not taken into account. We explore the potential of a joint analysis of tomographic galaxy ellipticity, galaxy Number Density, and ellipticity-Number Density cross-correlations to simultaneously constrain cosmology and self-calibrate unknown intrinsic alignment and galaxy bias contributions. Methods. We treat intrinsic alignments and galaxy biasing as free functions of scale and redshift and marginalise over the resulting parameter sets. Constraints on cosmology are calculated by combining the likelihoods from all two-point correlations between galaxy ellipticity and galaxy Number Density. The information required for these calculations is already available in a standard cosmic shear data set. We include contributions to these functions from cosmic shear, intrinsic alignments, galaxy clustering and magnification effects. Results. In a Fisher matrix analysis we compare our constraints with those from cosmic shear alone in the absence of intrinsic alignments. For a potential future large area survey, such as Euclid, the extra information from the additional correlation functions can make up for the additional free parameters in the intrinsic alignment and galaxy bias terms, depending on the flexibility in the models. For example, the dark energy task force figure of merit is recovered even when more than 100 free parameters are marginalised over. We find that the redshift quality requirements are similar to those calculated in the absence of intrinsic alignments.
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simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy Number Density correlations
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Benjamin Joachimi, S L BridleAbstract:Cosmic shear is a powerful method to constrain cosmology, provided that any systematic effects are under control. The intrinsic alignment of galaxies is expected to severely bias parameter estimates if not taken into account. We explore the potential of a joint analysis of tomographic galaxy ellipticity, galaxy Number Density, and ellipticity-Number Density cross-correlations to simultaneously constrain cosmology and self-calibrate unknown intrinsic alignment and galaxy bias contributions. We treat intrinsic alignments and galaxy biasing as free functions of scale and redshift and marginalise over the resulting parameter sets. Constraints on cosmology are calculated by combining the likelihoods from all two-point correlations between galaxy ellipticity and galaxy Number Density. The information required for these calculations is already available in a standard cosmic shear dataset. We include contributions to these functions from cosmic shear, intrinsic alignments, galaxy clustering and magnification effects. In a Fisher matrix analysis we compare our constraints with those from cosmic shear alone in the absence of intrinsic alignments. For a potential future large area survey, such as Euclid, the extra information from the additional correlation functions can make up for the additional free parameters in the intrinsic alignment and galaxy bias terms, depending on the flexibility in the models. For example, the Dark Energy Task Force figure of merit is recovered even when more than 100 free parameters are marginalised over. We find that the redshift quality requirements are similar to those calculated in the absence of intrinsic alignments.
S L Bridle - One of the best experts on this subject based on the ideXlab platform.
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simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy Number Density correlations
Astronomy and Astrophysics, 2010Co-Authors: Benjamin Joachimi, S L BridleAbstract:Aims. Cosmic shear is a powerful method to constrain cosmology, provided that any systematic effects are under control. The intrinsic alignment of galaxies is expected to severely bias parameter estimates if not taken into account. We explore the potential of a joint analysis of tomographic galaxy ellipticity, galaxy Number Density, and ellipticity-Number Density cross-correlations to simultaneously constrain cosmology and self-calibrate unknown intrinsic alignment and galaxy bias contributions. Methods. We treat intrinsic alignments and galaxy biasing as free functions of scale and redshift and marginalise over the resulting parameter sets. Constraints on cosmology are calculated by combining the likelihoods from all two-point correlations between galaxy ellipticity and galaxy Number Density. The information required for these calculations is already available in a standard cosmic shear data set. We include contributions to these functions from cosmic shear, intrinsic alignments, galaxy clustering and magnification effects. Results. In a Fisher matrix analysis we compare our constraints with those from cosmic shear alone in the absence of intrinsic alignments. For a potential future large area survey, such as Euclid, the extra information from the additional correlation functions can make up for the additional free parameters in the intrinsic alignment and galaxy bias terms, depending on the flexibility in the models. For example, the dark energy task force figure of merit is recovered even when more than 100 free parameters are marginalised over. We find that the redshift quality requirements are similar to those calculated in the absence of intrinsic alignments.
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simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy Number Density correlations
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Benjamin Joachimi, S L BridleAbstract:Cosmic shear is a powerful method to constrain cosmology, provided that any systematic effects are under control. The intrinsic alignment of galaxies is expected to severely bias parameter estimates if not taken into account. We explore the potential of a joint analysis of tomographic galaxy ellipticity, galaxy Number Density, and ellipticity-Number Density cross-correlations to simultaneously constrain cosmology and self-calibrate unknown intrinsic alignment and galaxy bias contributions. We treat intrinsic alignments and galaxy biasing as free functions of scale and redshift and marginalise over the resulting parameter sets. Constraints on cosmology are calculated by combining the likelihoods from all two-point correlations between galaxy ellipticity and galaxy Number Density. The information required for these calculations is already available in a standard cosmic shear dataset. We include contributions to these functions from cosmic shear, intrinsic alignments, galaxy clustering and magnification effects. In a Fisher matrix analysis we compare our constraints with those from cosmic shear alone in the absence of intrinsic alignments. For a potential future large area survey, such as Euclid, the extra information from the additional correlation functions can make up for the additional free parameters in the intrinsic alignment and galaxy bias terms, depending on the flexibility in the models. For example, the Dark Energy Task Force figure of merit is recovered even when more than 100 free parameters are marginalised over. We find that the redshift quality requirements are similar to those calculated in the absence of intrinsic alignments.
