Excited-configuration metastable level lifetimes of Cl-like MnIX and Fe X

Forbidden transitions from levels with P-3 and D-1 cores in excited configu rations of Cl-like Mn IX and Fe X have been isolated using interference fil ters. The fluorescence decay lifetimes of ions orbiting in a Kingdon ion tr ap were measured. New relativistic configuration interaction calculations o f relevant level lifetimes, to aid the analysis, based on B-spline basis se ts, are also presented. Line identifications and experimental lifetimes are Mn IX (D-4(7/2)-F-4(9/2)):363(-3/ + 7) nm; tau(Mn IX 3p(4)((3)p)3d(4)F(9/2 )) = 210 +/- 42 ms: tau(Fe X, 3p(4)(P-3)3d(4)F(9/2)) = 85.7 +/- 9.2 ms; tau (Fe X, 3p(4)(P-3)3d(4)F(7/2)) = 93 +/- 30 ms; and tau(Fe X, 3p(4)(D-1)3d(2) G(9/2)) = 17.8 +/- 3.1 ms.