Lifetime of the metastable 2P1/2 state of F-like Ar9+ isolated in a compact Penning trap

Multiply ionized atoms of a single charge state can be captured at low energy in a compact Penning trap, allowing the measurement of the radiative lifetime of an atomic state that decays via weakly allowed transitions. Such a measurement is reported here for the radiative decay lifetime of the metastable P-2(1/2) state in fluorinelike Ar9+, wherein the n = 2 shell has only one vacancy (hole) in a 2p orbital. Highly ionized atoms are extracted from an electron beam ion trap and guided into the ion capture apparatus. Upon capturing the Ar9+ ions, light from the magnetic-dipole transition is detected with a photomultiplier tube and counted with a multichannel scaler. Using this technique, the radiative lifetime of the metastable P-2(1/2) state in Ar9+ 1s(2) 2s(2) 2p(5) is measured to be tau = 9.31 +/- 0.08 ms, consistent with a previous intra-EBIT measurement.