The lifetimes of the ${1s}^{2}2s2p{}^3{P}_2$ level of Ar XV and ${1s}^2{2s}^{2}2p{}^2{P}_{3/2}$ of Ar XIV have been measured using metastable ${\mathrm{Ar}}^{14+}$ and ${\mathrm{Ar}}^{13+}$ ions produced by an electron cyclotron resonance ion source, which were subsequently separately captured into a Kingdon ion trap. The lifetime results are τ(Ar XV, 2s2p ${}^3{P}_2)=13.4\mathrm{}(7)\mathrm{}\mathrm{ms}$ and τ(Ar XIV,$2p{}^2{P}_{3/2})=9.12\mathrm{}(18)\mathrm{}\mathrm{ms}.$ Transition rates derived from the measured lifetimes differ significantly from both relativistic and nonrelativistic calculations of the $2s2p{}^3{P}_1{–}^3{P}_2$ $M1\mathrm{}$ transition rate of Ar XV, but are in reasonable agreement with calculations for the $2p{}^2{P}_{1/2}{–}^2{P}_{3/2}$ $M1\mathrm{}$ rate of Ar XIV.

• Received 11 March 1998

DOI:https://doi.org/10.1103/PhysRevA.58.1111