Spectra of N vi, O vii, F vii, and F viii in the grazing-incidence region

Focusing a Q-switched 1-GW ruby laser on a solid target and detecting the emitted radiation with a 2-m grazing incidence spectrograph, we observed He-like spectra of N vi, O vii, F viii, and Li-like F vii. More than 50 new lines have been observed and several others have been measured more accurately than previously. The ionization potentials of these ions, derived from the observations are I.P. N vi(2S) = 4 453 100 ± 200 cm−1; I.P. O vii(2S) = 5 962 800 ± 300 cm−1; and I.P. F viii(2S) = 7 694 000 ± 400 cm−1.