Measurements of line overlap for resonant photopumping of 4→4 transitions in highly charged nickel-like ions

Abstract

The wavelength of the 6${\mathit{f}}_{7/2}$→3${\mathit{d}}_{5/2}$d transition in several nickel-like ions has been measured on the Livermore electron-beam ion trap with a precision as high as 27 ppm in order to assess their utility in a resonant photopumping scheme to achieve x-ray lasing below 80 Å. An interpolation of the results is presented, which provides an estimate of the transition energies for ions between Dy (Z=66) and U (Z=92). The closest line coincidence was found for the 3d-6f transition in nickel-like Hf, which differs by 1.2 mÅ from the wavelength of the Ly-${\mathrm{\alpha }}_2$ transition in hydrogenic C1, and for the 3d-6f transition in T1, which differs by 0.8 mÅ from Ly-${\mathrm{\alpha }}_1$ in hydrogenic Ca.