Theoretical emission line ratios for [Fe III] and [Fe VII] applicable to the optical and infrared spectra of gaseous nebulae

AUTOR(ES)

Keenan, Francis P.

FONTE

National Academy of Sciences

RESUMO

Recent calculations of electron impact excitation rates and Einstein A-coefficients for transitions among the 3d6 levels of Fe III and among the 3d2 levels of Fe VII are used to derive theoretical emission line ratios applicable to the optical and infrared spectra of gaseous nebulae. Results for [Fe III] are generated for electron temperatures Te = 7,000–20,000 K and densities Ne = 102-108 cm−3, whereas those for [Fe VII] are provided for Te = 10,000–30,000 K and Ne = 102-108 cm−3. The theoretical line ratios are significantly different in some instances from earlier calculations and resolve discrepancies between theory and observation found for the planetary nebulae IC 4997 and NGC 7027.

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