Experimental M1 Transition Rates of Coronal Lines from Ar<scp>x</scp>, Ar<scp>xiv</scp>, and Ar<scp>xv</scp>

Abstract

Transition probabilities of three magnetic dipole (M1) transitions in multiply charged ions of Ar have been measured using the Livermore electron-beam ion trap. Two of the transitions are in the ground configurations of Ar XIV (B-like) and Ar IX (F-like), and are associated with the coronal lines at 4412.4 and 5533.4 Å, respectively. The third is in the excited 2s2p configuration of Be-like Ar XV and produces the coronal line at 5943.73 Å. Our results for the three atomic level lifetimes are 9.32 ± 0.12 ms for the Ar X 2s22p5 2P level, 9.70 ± 0.15 ms for the Ar XIV 2s22p2P level, and 15.0 ± 0.8 ms for the Ar XV 2s2p3P level. These results differ significantly from earlier measurements and are the most accurate ones to date.