Lifetime determination of the Fe XIV 3s²3p ²P_3∕2^o metastable level

The lifetime of the 3s²3p ²P_3∕2^o first excited energy level of Fe XIV (Al like) was measured at the Heidelberg electron beam ion trap by monitoring its optical decay to the ground state by a magnetic dipole (M1) forbidden transition at λ=530.29 nm (green coronal line), a well-known line in stellar spectra. A new trapping scheme has been applied. Possible systematic effects were investigated by studying the dependence of the decay curves on various trapping conditions with high statistical significance. The result of 16.726_−0.010^+0.020 ms shows an unexplained discrepancy in the average value of existing theoretical predictions. The inclusion of the electron anomalous magnetic moment within the theoretical calculations increases this disagreement, thus pointing at other possible origins of this discrepancy.