Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron-impact excitation of N$^{3+}$ using the B-spline R-matrix
  method: Importance of the target structure description and the size of the
  close-coupling expansion   There are major discrepancies between recent ICFT (Intermediate Coupling
Frame Transformation) and DARC (Dirac Atomic R-matrix Code) calculations
(Fern\'andez-Menchero et al. 2014, Astron. Astroph. 566 A104, Aggarwal et al.
2016 Mon. Not. R Astr. Soc. 461 3997) regarding electron-impact excitation
rates for transitions in several Be-like ions, as well as claims that the DARC
calculations are much more accurate and the ICFT results might even be wrong.
To identify possible reasons for these discrepancies and to estimate the
accuracy of the various results, we carried out independent B-Spline R-Matrix
(BSR) calculations for electron-impact excitation of the Be-like ion N$^{3+}$.
Our close-coupling expansions contain the same target states (238 levels
overall) as the previous ICFT and DARC calculations, but the representation of
the target wave functions is completely different. We find close agreement
among all calculations for the strong transitions between low-lying states,
whereas there remain serious discrepancies for the weak transitions as well as
for transitions to highly excited states. The differences in the final results
for the collision strengths are mainly due to differences in the structure
description, specifically the inclusion of correlation effects, rather than the
treatment of relativistic effects or problems with the validity of the three
methods to describe the collision. Hence there is no indication that one
approach is superior to another, until the convergence of both the target
configuration and the close-coupling expansions have been fully established.

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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th