English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Recent state-of-the-art calculations of A-values and electron impactexcitation rates for Fe III are used in conjunction with the Cloudy modelingcode to derive emission line intensity ratios for optical transitions among thefine-structure levels of the 3d$^6$ configuration. A comparison of these withhigh resolution, high signal-to-noise spectra of gaseous nebulae reveals thatprevious discrepancies found between theory and observation are not fullyresolved by the latest atomic data. Blending is ruled out as a likely cause ofthe discrepancies, because temperature- and density-independent ratios (arisingfrom lines with common upper levels) match well with those predicted by theory.For a typical nebular plasma with electron temperature $T_{\rm e} = 9000$ K andelectron density $\rm N_{e}=10^4 \, cm^{-3}$, cascading of electrons from thelevels $\rm ^3G_5$, $\rm ^3G_4$ and $\rm ^3G_3$ plays an important role indetermining the populations of lower levels, such as $\rm ^3F_4$, which providethe density diagnostic emission lines of Fe III, such as $\rm ^5D_4$ - $\rm^3F_4$ at 4658 \AA. Hence further work on the A-values for these transitions isrecommended, ideally including measurements if possible. However, some Fe IIIratios do provide reliable $N_{\rm e}$-diagnostics, such as 4986/4658. The FeIII cooling function calculated with Cloudy using the most recent atomic datais found to be significantly greater at $T_e$ $\simeq$ 30000 K than predictedwith the existing Cloudy model. This is due to the presence of additionalemission lines with the new data, particularly in the 1000--4000 \AA\wavelength region.

Emission line ratios of Fe III as astrophysical plasma diagnostics