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The spectrum of singly ionized iron, Fe II, has been recorded in the wavelength regions 900-2200 Å and 4800-11200 Å by means of a pulsed hollow-cathode discharge. In the vacuum-ultraviolet region identifications are given for 1358 lines. The list for the region above 4800 Å contains 1564 observed lines, 1341 of which are identified. In the 2200-4800 Å range about 350 lines in the line list published by Dobbie in 1938 have been newly identified. On the basis of interferometric measurements made by G. Norlén of 350 lines a recalculation of the whole term system has been performed. Altogether 576 energy levels are now known in Fe II, some 250 of which are the results of the present analysis. The levels belong to the configurations (3d6)4s, 5s, 6s, 4p, 5p, 3d, 4d, 5d, 4f and (3d54s)4s, 5s, 4p, 4d and 3d54p2. Theoretical predictions of the structure of the (3d64p + 3d65p + 3d54s4p) complex by J. Sinzelle and J. F. Wyart are in good agreement with the observations. The ionization energy has been determined to 130 563 ± 10 cm-1.
Sveneric Johansson (Sun,) studied this question.