Term Analysis of Fe VI

Abstract

The spectrum of Fe VI has been observed by using a vacuum sliding-spark discharge and the 10.7-m grazing-incidence spectrograph and the 10.7-m normal-incidence spectrograph at the National Bureau of Standards, Washington. More than 400 lines have been classified in the region 250-1 580 Å. All terms of the configurations 3d ³, 3d ²4s and 3d ²4p, except 3d ²(¹ S)4s ² S have been established. The estimated uncertainty of the level values is ±0.4 cm^-1. The 3d ³, 3d ²4s and 3d ²4p level structure has been theoretically interpreted. The energy parameters determined from a least-squares fit of the observed level values are compared with Hartree-Fock calculations. From the complete set of 3d ³ levels all forbidden lines of Fe VI from 1 387 to 10 000 Å have been predicted. All but two lines in the spectrum of the star RR Telescopii previously identified as forbidden Fe VI lines have been confirmed and 6 of the otherwise unexplained lines have been identified as [Fe VI].