Lifetime of the metastable P1/22 state of F-like Ar9+ isolated in a compact Penning trap

Abstract

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 $^{2}P_{1/2}$ state in fluorinelike ${\mathrm{Ar}}^{9+}$, 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 ${\mathrm{Ar}}^{9+}$ 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 $^{2}P_{1/2}$ state in ${\mathrm{Ar}}^{9+}\phantom{\rule{4pt}{0ex}}1{s}^{2}\phantom{\rule{0.16em}{0ex}}2{s}^{2}\phantom{\rule{0.16em}{0ex}}2{p}^{5}$ is measured to be $\ensuremath{\tau}=9.31\ifmmode\pm\else\textpm\fi{}0.08$ ms, consistent with a previous intra-EBIT measurement.