EUV intercombination transition rates in Be-like nitrogen and oxygen ions measured at a heavy-ion storage ring

The electric dipole intercombination decay rate of the 2s2p 3Po1 level in the Be-like ions N3+ and O4+ has been measured with ions circulating in a heavy-ion storage ring. The observation employed three devices in parallel, two different VUV photon detectors and a residual gas recoil ion detector. The measured transition probabilities of (578 ± 3.3) s-1 for N3+ (level lifetime τ = 1.73 ± 0.01 ms) and of (2315 ± 50) s-1 for O4+ (τ = 0.432 ± 0.009 ms), corroborate the results of recent calculations and improve the precision with which the isoelectronic trend can be established