New Identifications of Si VIII and S X Lines in the Solar Coronal Spectrum Measured by SOHO/SUMER

Abstract

This paper reports the identification of 14 lines in the solar coronal spectrum as high-excitation 2s²2p²3s-2s²2p²3p and 2s²2p²3p-2s²2p²3d transitions in Si VIII and S X (N I isoelectronic sequence). The analysis combines solar spectra, recorded by the SUMER (Solar Ultraviolet Measurement of Emitted Radiation) instrument on board the Solar and Heliospheric Observatory (SOHO) satellite, with laboratory data obtained with the beam-foil technique. Theoretical gA values and branching ratios for the observed lines, based on semiempirical calculations, are also presented. Intensity ratios between the newly identified high-excitation transitions and known forbidden transitions within the 2s²2p³ ground configuration can be used in determining coronal plasma temperatures in the 70-120 eV range.