Atomic-Lifetime Measurements for Neutral and Ionized Sodium and Potassium

Abstract
The beam-foil excitation technique has been used to measure mean lives of excited atomic states in Na i, Na ii, Na iii, K ii, and K iii. In agreement with earlier measurements, a mean life of 17.3±1.0×10−9 s has been obtained for the unresolved 3s–3p doublet transition in Na i. The mean lives of the 3p5 4p fine-structure levels in K ii have been measured and compared with earlier measurements in Ar i. Based on the observed mean lives, two spectral lines (2387 and 2394 Å), previously assigned as Na ii lines, have been assigned as transitions in Na iii.