Unresolved Dielectronic Satellites of the Resonance Line of Heliumlike Iron (Fe XXV)

High-resolution spectra of Fe xxv have been observed from Princeton Large Torus tokamak discharges and are used for a detailed comparison with theoretical predictions of Bely-Dubau, Gabriel, and Volonté for the ($1s^{2}nl-1s2pnl$, $n>~3$) dielectronic satellites at 1.85 Å. The theory predicts a significant apparent broadening of the resonance lines of high-$Z$ heliumlike ions in high-temperature plasmas due to the dielectronic capture of electrons into outer atomic shells. The experimental results and theoretical predictions are in good general agreement.