Oscillator strengths of the2sS122−2pP12,32o2transitions in Fe xxiv and the2s2S01−2s2pP1o3transition in Fe xxiii

Abstract

We have used the beam-foil technique to measure the mean lives of the upper levels of: (i) the $2s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-2p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^o{}_{}{}^{}$ resonance transitions (at 255 and 192 Å) in lithiumlike Fe xxiv and (ii) the $2s^2{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}-2s2p{}_{}{}^3{}_{}{}^{}P_1^o{}_{}{}^{}$ intersystem transition (at 264 Å) in berylliumlike Fe xxiii. The measured mean lives are $\tau \left(2p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^o{}_{}{}^{}\right)=0.55\mathrm{}\pm 0.02$, $\tau \left(2p{}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^o{}_{}{}^{}\right)=0.235\mathrm{}\pm 0.01$, and $\tau \left(2s2p{}_{}{}^3{}_{}{}^{}P_1^o{}_{}{}^{}\right)=13\mathrm{}\pm 4$ ns. Oscillator strengths derived from the Fe xxiv results are in good agreement with recent relativistic multiconfiguration Hartree-Fock (MCHF) "length" gauge calculations; the Fe xxiii result is not in agreement with these MCHF calculations, but appears to be in agreement with recent intermediate coupling calculations.