Assessment of Atomic Data: Problems and Solutions

Abstract

For the reliable analysis and modelling of astrophysical, laser-produced and fusion plasmas, atomic data are required for a number of parameters, including energy levels, radiative rates and electron impact excitation rates. Such data are desired for a range of elements (H to W) and their many ions. However, measurements of atomic data, mainly for radiative and excitation rates, are not feasible for many species and therefore calculations are needed. For some ions (such as of C, Fe and Kr) there are a variety of calculations available in the literature, but often they significantly differ from one another. Therefore, there is a great demand from the user community to have data 'assessed' for accuracy so that they can be confidently applied to the modelling of plasmas. In this paper we highlight the difficulties in assessing atomic data and offer some solutions for improving the accuracy of calculated results.

Discrepancies in Atomic Data and Suggestions for Their Resolutions

“…In all such cases the theoretical results are very close to the available measurements. This reinforces our earlier conclusion [1] that all codes are not useful for all applications, significant discrepancies between theory and measurements should not be ignored, and the choice of a code is very important and should be based on: (i) the ion concerned, (ii) the accuracy desired, and (iii) the application in mind. Furthermore, what configurations to include in a calculation is equally important, and should be based on a fair balance of even and odd CSFs as deliberated by Froese Fischer [17], and their energy ranges as emphasised by us [19,20].…”

“…Discrepancies in the Υ results, obtained with the DARC and ICFT codes, until 2012 have mostly been discussed in our earlier paper [1], and therefore these are not repeated here. However, just to recapitulate large discrepancies had been noted (and highlighted) for H-like, He-like, Li-like, and some Mg-like ions -see [1] for problems and specific references. Here we mostly focus on transitions in Be-like (and some other specific) ions which have been under discussion in the recent literature.…”

“…During the past few decades a wide range of methods and codes have been developed to calculate the desired data -see for example [1] and references therein. However, often there are large discrepancies among different calculations for almost all parameters, as has already been discussed in detail earlier [1]. Such discrepancies make it difficult for modellers to apply the data with confidence, particularly when neither measurements are available to compare with nor the calculations can be easily repeated to verify the accuracy.…”

Comment on “Electron impact excitation and ionization cross section of tungsten ions, W44+” by El-Maaref et al. [J. Quant. Spectrosc. Radiat. Transfer 2019, 224:147]

“…Neither is it possible for a single other qualified person (or a group) because a large amount of atomic data are almost continuously being generated and reported. Therefore, as has already been suggested [4], it is upon the producers of data to make assessments of accuracy through rigorous checks and comparisons. It is a general tendency to believe that the latest reported data are more accurate than those already available in the literature, but it can be highly misleading as presently seen for the case of W XLV, and several other ions earlier [6].…”

Radiative rates for E1, E2, M1, and M2 transitions among the 3s23p5, 3s3p6, and 3s23p43d configurations of Cl-like W LVIII

“…The need for atomic data for W ions has become more urgent due to the developing ITER project. However, there are two requirements from the user community, namely, the data should be generated for a significantly large model [6] and be reliable [7]. A complete set of data from a large model takes into account cascading effects, while reliability (based on rigorous tests) provides confidence to the users.…”