Abstract
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, 3p63d2, and 20 lines from 1010 Å to 1362 Å as 3d4s-3d4p combinations. All 13 levels of 3d2 and 3d4s have been observed as well as 141 levels of the 3d4p, 3dnf (n = 4-10), 3p53d3 and 3p53d24s configurations. The level structure of 3d2, 3d4s, 3d4f, 3d5f, 3d6f and 3p53d24s 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 3dnf series to 1 008 000 ± 100 cm-1 (124.98 ± 0.1 eV).Predicted wavelengths and intensities of the forbidden transitions within 3d2 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.
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