Measurement of the lifetime of the3 P 2 and4 P 5/2 states in Ar16+ and Ar15+

Abstract

Promptly decaying levels in Li- and Be-like Ar could be identified in the delayed x-ray and electron spectrum in addition to the four known metastable (1s2s)1S0, (1s2s)3S1, (1s2p)3P2, and (1s2s2p)4P5/2 states in He- and Li-like systems. The states having lifetimes of about 10−14s still contribute to the spectrum observed 10−9s after the ions have passed a foil. This observation is explained by cascading processes from states of high principal quantum numbern≧14. The measured lifetime of the4P5/2 state subtracting the contribution of cascades is (0.594±0.016) ns and slightly larger than the theoretically predicted value of 0.563 ns. The3P2 state is depopulated at short distances behind the foil by cascading processes. Its measured lifetime of (1.44±0.08) ns compares to a theoretical value of 1.48 ns.