Determination of the 3d(3)4d and 3d(3)5s configurations of FeV

The analysis of the spectrum of four times ionized iron, Fe V, has led to t he determination of the 3d(3)4d and 3d(3)5s configurations. From 975 classi fied lines in the region 645-1190 Angstrom we have established 123 of 168 t heoretically possible 3d(3)4d levels and 26 of 38 possible 3d(3)5s levels. The estimated accuracy of values of energy levels of these two configuratio ns is about 0.7 cm(-1) and 1.0 cm(-1), respectively. The level structure of the system of the 3d(4), 3d(3)4s, 3d(3)4d and 3d(3)5s configurations has b een theoretically interpreted and the energy parameters have been determine d by a least squares fit to the observed levels. A comparison of parameters in Cr III and Fe V ions is given.