Consideration of the forbidden lines of iron in the states from Fe0 to Fe6+

The iron atom which has a fairly high cosmic abundance presents the great interest of appearing in a wide variety of stars and nebulae, at many stages of ionization, and of revealing forbidden transitions in emission in many of these ionization stages. The present paper discusses the following topics :
(a) the case of the as yet undiscovered forbidden lines of neutral iron (Fe0) ;
(b) some recently acquired astronomical information on the forbidden lines of the stages Fe+ to Fe6+ ;
(c) general considerations on the important information revealed by these forbidden lines of iron on the physical structure and excitation mechanisms which are present in the emission line stars of early and late types.
For lack of time we give only a very summarized version of our paper ; a complete text will appear later.