Lifetime measurements of core-excited quartet levels in Na i

In a recent spectroscopic study [D. E. Holmgren et al., Phys. Rev. A 31, 677 (1985)], many metastable core-excited quartet levels in Na i have been identified, and based on calculated decay rates (both radiative and autoionizing) some of these levels have been suggested for use in an extreme ultraviolet (xuv) laser. In order to test the theoretical calculations we have used the beam-foil technique to determine experimental lifetimes for eight quartet levels in the core-excited configurations 2p⁵3s3d and 2p⁵3s4s. The agreement between theory and experiment is within a factor of 2, but with systematic discrepancies.