Precision spectroscopy on stored, highly charged ions using free-electron-laser radiation

The feasibility of a precision measurement of the ground-state hyperfine structure of hydrogenlike sodium is considered, based on the use of a proposed rf-linac extreme-UV free-electron laser. The laser would be used for intensity-pumping population redistribution within the ground-state sublevels of the stored ions, through excitation of the 1s--2p transition near 1 nm. The magnetic dipole transition between the hyperfine-structure sublevels would be detected by changes in the mean number of scattered 1.2-keV photons following the low-frequency transition