CHIANTI-An Atomic Database for Emission Lines. V. Comparison with an Isothermal Spectrum Observed with SUMER

CHIANTI is a database consisting of critically evaluated atomic data and transition probabilities necessary to analyze spectral observations of optically thin plasmas. Previous papers described the content of the database and compared it to a solar active region spectrum between 170 and 450 Å. The aim of the present paper is to compare CHIANTI predictions to off-disk spectral observations of the solar corona between 500 and 1500 Å. The observed spectra were recorded by the SUMER instrument on board the Solar and Heliospheric Observatory using the full spectral range allowed by the instrument. Earlier works have demonstrated that the particular emitting plasma is isothermal at a temperature of 1.35×10⁶ K, making it ideal for the assessment of the accuracy of the CHIANTI database. This assessment of the CHIANTI database allowed us (1) to select lines and ions for which the agreement between theory and observation is good, (2) to identify several lines which are blended, and (3) to stress inconsistencies between a few lines and theory, thus showing where improvements to atomic data and transition probabilities are necessary.