New Identifications of Mn VII and Fe VIII Lines Belonging to Transitions of the Type 3p⁶4p-3p⁶4d and 3p⁵3d²-3p⁶4d

Abstract

The Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer aboard the Solar and Heliospheric Observatory (SOHO) recorded a large number of spectra in the 500-1600 Å region. Many of the detected spectral lines have been identified as transitions in ions from elements with low-to-moderate atomic numbers (Z<=20). However, a substantial number of lines remained unidentified. We postulated that some of the unidentified lines are transitions between excited configurations in Fe⁺⁷. Unfortunately, Cr⁺⁵ was the last ion in the K I isoelectronic sequence where the envisioned types of transitions were previously identified. In this paper we report new identifications, in laboratory-generated spectra, of transitions between excited configurations in Mn⁺⁶ and Fe⁺⁷, two additional ions along the K I isoelectronic sequence. Since the elemental abundance of manganese in the solar atmosphere is very low, no Mn VII lines were identified in the SUMER spectra; however, the laboratory-identified Fe VIII lines were found to be present in the SUMER quiet-Sun spectra recorded above the solar limb and in sunspot spectra recorded on the solar disk.