Spectra of Fe, Co, Ni, and Cu Isoelectronic with Na i and Mg i

Abstract

Highly ionized spectra of Fe, Co, Ni, and Cu belonging to the Na I and Mg I isoelectronic sequences are discussed. For the Na I-type spectra about 48 lines between 20 and 400 Å are classified for the first time. The wavelengths of some 20 other previously classified lines are given with greater accuracy. The measurement of the n = 3 transitions and of the higher-series lines has enabled us to construct the energy-level table and to obtain accurate least-square fits for the series limits and ionization potentials. For the Mg I sequence, nine new lines are classified in Fe xv and Co xvi and 36 lines in Ni xvii and Cu xviii. Not enough lines are yet classified to deduce the values of the energy levels.