Analysis of 4d-4f transitions in Co II

The high resolution Fourier-transform emission spectrum from a cobalt-neon hollow cathode lamp has been studied in the region 4682-6135 A (16300-21360 cm-1). Of the 48 levels of the Co II 3d7(4F)4f subconfiguration, 46 are found by means of 329 newly identified transitions to the levels of the 3d7(4F)4d subconfiguration. These lines account for the majority of previously unclassified transitions in this spectral region. Revised values of 33 levels of the 3d7(4F)4d subconfiguration are given and the five missing levels are found. The accuracy of the energy levels is a few mK (1 mK = 0.001 cm-1). JK coupling is used to represent the 4f levels and the suitability of this is shown by applying the quadrupolic approximation. A classified linelist of the observed 4d-4f transitions is given with wavenumbers, accurate to 0.001 cm-1 for strong lines, and the observed intensities. (orig.)