Measurement of radiative lifetimes of low-lying excited states in sodiumlike, fluorinelike, and oxygenlike iron

Abstract

We have used the beam-foil technique to study the spectra of Fe XVI to Fe XX ions in the far vacuum ultraviolet range and to measure the mean lives of the upper levels of the $3s-3p$ and $3p-3d$ transitions in sodiumlike Fe XVI, the $2s^{2}2p^5{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^o{}_{}{}^{}-2s2\mathrm{}{p}^6{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ resonance transition in F-like Fe XVIII, and the $2s^{2}2p^4{}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}-2s2p^5{}_{}{}^3{}_{}{}^{}P_2^o{}_{}{}^{}$ resonance transition in O-like Fe XIX. Deduced oscillator strengths are in good agreement with relativistic calculations. Tentative identifications are proposed for neonlike Fe XVII.