Plasma Diagnostics

Joachim Köppen Kiel Dec.2016

Line: Wavelength [A] Intensity
[O II] 3728
[Ne III] 3869
[O III] 4363
He II 4686
H I 4861
[O III] 5007
[N II] 5755
He I 5876
[S III] 6312
H I 6563
[N II] 6584
[S II] 6717
[S II] 6731
[Ar III] 7135
[O II] 7325

Elemental abundances

This utility permits to analyse the emission line spectra of ionized gaseous nebulae. It assumes that the spectrum comes from homogeneous and isothermal plasma with a certain degree of ionization. From several lines intensity ratios one determines the basic parameters:
  • interstellar extinction from Hα and Hβ
  • electron temperature [K] in the O++ zone from [O III] 5007 and 4363
  • electron temperature [K] in the O+ zone from [N II] 6584 and 5755
  • electron density [cm-3] from [S II] 6717 and 6731
An iteration assures the consistency of these values. Next, from the lines of each ion, the ionic abundances are derived with the electron density and temperature. Finally, the elemental abundances are determined, using empirical ionization correction factors, which compensate for unobserved ions.

How to use it:
enter the measured line fluxes - of as many lines as available!
click analyse button.
the estimated reliability of displayed values is indicated by the background colour:
  • white: everything OK
  • yellow: minor problems; e.g. default temperatures need to be assumed
  • orange: serious problems in the analysis
  • red: unreliable
  • grey: rubbish; e.g. this element has no observed line!
This colour code tracks the propagation of errors in the analysis, such as how a missing line necessary for temperature determination affects all subsequent values. It is based on personal estimates and experience, and should be taken as a rough indication only!
clicking the extinction, temperature, and density buttons allows to use fixed values, e.g. to explore the sensitivity of the results on the accuracy of these values.

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last update: Dec. 2016 J.Köppen