Term Analysis of Fe IV and Identifiction of [Fe IV] in RR Telescopii

Abstract

From an experimental investigation of the fourth spectrum of iron we report the levels of $${3}^{{d}^{4}}(^{5}D)4s \,\text{and} \,3^{{d}^{4}}(^{5}D)4p$$ as well as the set of $$3^{{d}^{5}}$$ levels. This set permits us to make a practically exhaustive prediction of the spectrum of forbidden Fe IV lines and to explain the origin of 17 emission lines in RR Telescopii.