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154 KiB

Open AccessEditorial

Notes on Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities

by Hyun-Kyung Chung, Per Jönsson and Alexander Kramida

Atoms 2013, 1(3), 14-16; https://doi.org/10.3390/atoms1030014 - 8 Aug 2013

Cited by 1 | Viewed by 6226

Abstract

Atomic structure and transition probabilities are fundamental physical data required in many fields of science and technology. Atomic physics codes are freely available to other community users to generate atomic data for their interest, but the quality of these data is rarely verified. [...] Read more.

Atomic structure and transition probabilities are fundamental physical data required in many fields of science and technology. Atomic physics codes are freely available to other community users to generate atomic data for their interest, but the quality of these data is rarely verified. This special issue addresses estimation of uncertainties in atomic structure and transition probability calculations, and discusses methods and strategies to assess and ensure the quality of theoretical atomic data. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

83 KiB

Open AccessEditorial

Special Issue on Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities

by Per Jönsson and Hyun-Kyung Chung

Atoms 2013, 1(2), 13; https://doi.org/10.3390/atoms1020013 - 21 Jun 2013

Cited by 1 | Viewed by 5222

Abstract

There exist several codes in the atomic physics community to generate atomic structure and transition probabilities freely and readily distributed to researchers outside atomic physics community, in plasma, astrophysical or nuclear physics communities. Users take these atomic physics codes to generate the necessary [...] Read more.

There exist several codes in the atomic physics community to generate atomic structure and transition probabilities freely and readily distributed to researchers outside atomic physics community, in plasma, astrophysical or nuclear physics communities. Users take these atomic physics codes to generate the necessary atomic data or modify the codes for their own applications. However, there has been very little effort to validate and verify the data sets generated by non-expert users. [...] Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

Research

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242 KiB

Open AccessArticle

Estimating Relative Uncertainty of Radiative Transition Rates

by Daniel E. Kelleher

Atoms 2014, 2(4), 382-390; https://doi.org/10.3390/atoms2040382 - 25 Nov 2014

Cited by 2 | Viewed by 4481

Abstract

We consider a method to estimate relative uncertainties of radiative transition rates in an atomic spectrum. Few of these many transitions have had their rates determined by more than two reference-quality sources. One could estimate uncertainties for each transition, but analyses with only [...] Read more.

We consider a method to estimate relative uncertainties of radiative transition rates in an atomic spectrum. Few of these many transitions have had their rates determined by more than two reference-quality sources. One could estimate uncertainties for each transition, but analyses with only one degree of freedom are generally fraught with difficulties. We pursue a way to empirically combine the limited uncertainty information in each of the many transitions. We “pool” a dimensionless measure of relative dispersion, the “Coefficient of Variation of the mean,” \(C_{V}^{n} \equiv s/(\bar{x}\sqrt{n})\). Here, for each transition rate, “s” is the standard deviation, and “\(\bar{x}\)” is the mean of “n” independent data sources. \(C_{V}^{n}\) is bounded by zero and one whenever the determined quantity is intrinsically positive.) We scatter-plot the \(C_{V}^{n} \)as a function of the “line strength” (here a more useful radiative transition rate than transition probability). We find a curve through comparable \(C_{V}^{n} \)as that envelops a specified percentage of the \(C_{V}^{n} \)s (e.g. 95%). We take this curve to represent the expanded relative uncertainty of the mean. The method is most advantageous when the number of determined transition rates is large while the number of independent determinations per transition is small. The transition rate data of Na III serves as an example. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

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2768 KiB

Open AccessArticle

AtomPy: An Open Atomic Data Curation Environment for Astrophysical Applications

by Claudio Mendoza, Josiah S. Boswell, David C. Ajoku and Manuel A. Bautista

Atoms 2014, 2(2), 123-156; https://doi.org/10.3390/atoms2020123 - 2 May 2014

Cited by 6 | Viewed by 11766

Abstract

We present a cloud-computing environment, referred to as AtomPy, based on Google-Drive Sheets and Pandas (Python Data Analysis Library) DataFrames to promote community-driven curation of atomic data for astrophysical applications, a stage beyond database development. The atomic model for each ionic species is [...] Read more.

We present a cloud-computing environment, referred to as AtomPy, based on Google-Drive Sheets and Pandas (Python Data Analysis Library) DataFrames to promote community-driven curation of atomic data for astrophysical applications, a stage beyond database development. The atomic model for each ionic species is contained in a multi-sheet workbook, tabulating representative sets of energy levels, A-values and electron impact effective collision strengths from different sources. The relevant issues that AtomPy intends to address are: (i) data quality by allowing open access to both data producers and users; (ii) comparisons of different datasets to facilitate accuracy assessments; (iii) downloading to local data structures (i.e., Pandas DataFrames) for further manipulation and analysis by prospective users; and (iv) data preservation by avoiding the discard of outdated sets. Data processing workﬂows are implemented by means of IPython Notebooks, and collaborative software developments are encouraged and managed within the GitHub social network. The facilities of AtomPy are illustrated with the critical assessment of the transition probabilities for ions in the hydrogen and helium isoelectronic sequences with atomic number Z ≤ 10. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

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832 KiB

Open AccessArticle

Assessing Uncertainties of Theoretical Atomic Transition Probabilities with Monte Carlo Random Trials

by Alexander Kramida

Atoms 2014, 2(2), 86-122; https://doi.org/10.3390/atoms2020086 - 14 Apr 2014

Cited by 44 | Viewed by 6190

Abstract

This paper suggests a method of evaluation of uncertainties in calculated transition probabilities by randomly varying parameters of an atomic code and comparing the results. A control code has been written to randomly vary the input parameters with a normal statistical distribution around [...] Read more.

This paper suggests a method of evaluation of uncertainties in calculated transition probabilities by randomly varying parameters of an atomic code and comparing the results. A control code has been written to randomly vary the input parameters with a normal statistical distribution around initial values with a certain standard deviation. For this particular implementation, Cowan’s suite of atomic codes (R.D. Cowan, The Theory of Atomic Structure and Spectra, Berkeley, CA: University of California Press, 1981) was used to calculate radiative rates of magnetic-dipole and electric-quadrupole transitions within the ground configuration of titanium-like iron, Fe V. The Slater parameters used in the calculations were adjusted to fit experimental energy levels with Cowan’s least-squares fitting program, RCE. The standard deviations of the fitted parameters were used as input of the control code providing the distribution widths of random trials for these parameters. Propagation of errors through the matrix diagonalization and summation of basis state expansions leads to significant variations in the resulting transition rates. These variations vastly differ in their magnitude for different transitions, depending on their sensitivity to errors in parameters. With this method, the rate uncertainty can be individually assessed for each calculated transition. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

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939 KiB

Open AccessArticle

Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities: An Experimenter’s View

by Elmar Träbert

Atoms 2014, 2(1), 15-85; https://doi.org/10.3390/atoms2010015 - 19 Mar 2014

Cited by 23 | Viewed by 7149

Abstract

The interpretation of atomic observations by theory and the testing of computational predictions by experiment are interactive processes. It is necessary to gain experience with “the other side” before claims of achievement can be validated and judged. The discussion covers some general problems [...] Read more.

The interpretation of atomic observations by theory and the testing of computational predictions by experiment are interactive processes. It is necessary to gain experience with “the other side” before claims of achievement can be validated and judged. The discussion covers some general problems in the field as well as many specific examples, mostly organized by isoelectronic sequence, of what level of accuracy recently has been reached or which atomic structure or level lifetime problem needs more attention. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

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308 KiB

Open AccessArticle

Evaluation and Comparison of the Configuration Interaction Calculations for Complex Atoms

by Charlotte Froese Fischer

Atoms 2014, 2(1), 1-14; https://doi.org/10.3390/atoms2010001 - 19 Mar 2014

Cited by 25 | Viewed by 5072

Abstract

Configuration interaction (CI) methods are the method of choice for the determination of wave functions for complex atomic systems from which a variety of atomic properties may be computed. When applied to highly ionized atoms, where few, if any, energy levels from observed [...] Read more.

Configuration interaction (CI) methods are the method of choice for the determination of wave functions for complex atomic systems from which a variety of atomic properties may be computed. When applied to highly ionized atoms, where few, if any, energy levels from observed wavelengths are available, the question arises as to how a calculation may be evaluated. Many different codes are available for such calculations. Agreement between the results from different codes in itself is not a check on accuracy, but may be due to a similarity in the computational procedures. This paper reviews basic theory, which, when applied in a systematic manner, can be the basis for the evaluation of accuracy. Results will be illustrated in the study of 4s24p5 (odd) and 4s24p44d (even) levels in W39+ and the transitions between them. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

Review

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862 KiB

Open AccessReview

Validation and Implementation of Uncertainty Estimates of Calculated Transition Rates

by Jörgen Ekman, Michel R. Godefroid and Henrik Hartman

Atoms 2014, 2(2), 215-224; https://doi.org/10.3390/atoms2020215 - 15 May 2014

Cited by 80 | Viewed by 5998

Abstract

Uncertainties of calculated transition rates in LS-allowed electric dipole transitions in boron-like O IV and carbon-like Fe XXI are estimated using an approach in which differences in line strengths calculated in length and velocity gauges are utilized. Estimated uncertainties are compared and validated [...] Read more.

Uncertainties of calculated transition rates in LS-allowed electric dipole transitions in boron-like O IV and carbon-like Fe XXI are estimated using an approach in which differences in line strengths calculated in length and velocity gauges are utilized. Estimated uncertainties are compared and validated against several high-quality theoretical data sets in O IV, and implemented in large scale calculations in Fe XXI. Full article

(This article belongs to the Special Issue Critical Assessment of Theoretical Calculations of Atomic Structure and Transition Probabilities)

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