Term Analysis of Fe VII

The spectrum of six times ionized iron, Fe VII, has been observed by using low- and high-voltage sliding sparks. The spectrograms were recorded on the 10.7 m normal incidence and 10.7 m grazing incidence spectrographs at the National Bureau of Standards, Washington, and on the 3 m normal incidence spectrograph at our institute. More than 400 lines have been classified in the region 104-270 Å as transitions to the ground configuration, 3 p 6 3 d 2 , and 20 lines from 1010 Å to 1362 Å as 3 d 4 s -3 d 4 p combinations. All 13 levels of 3 d 2 and 3 d 4 s have been observed as well as 141 levels of the 3 d 4 p , 3 dnf ( n = 4-10), 3 p 5 3 d 3 and 3 p 5 3 d 2 4 s configurations. The level structure of 3 d 2 , 3 d 4 s , 3 d 4 f , 3 d 5 f , 3 d 6 f and 3 p 5 3 d 2 4 s has been theoretically interpreted and the energy parameters, determined from least-squares fits to the observed level values, are compared with Hartree-Fock calculations. The ionization energy is found from the 3 dnf series to 1 008 000 ± 100 cm -1 (124.98 ± 0.1 eV). Predicted wavelengths and intensities of the forbidden transitions within 3 d 2 are collected in a list containing 17 entries from 1490 to 8729 Å. A comparison with Thackeray's line list for RR Telescopii shows an excellent agreement as regards both wavelengths and intensities.