Isotope shifts in odd and even energy levels of the neutral and singly ionised gadolinium atom

Isotope shift studies in the gadolinium spectra have been extended in the region 4140–4535 Å. Isotope shift Δσ(156–160) have been measured in 315 lines of the neutral and singly ionised galolinium atom using a recording Fabry—Perot Spectrometer and gadolinium samples enriched in ¹⁵⁶Gd and ¹⁶⁰Gd isotopes. Some of the Gd I lines studied involve transitions from newly identified high odd levels of 4f⁸6s 6p, 4f⁷5d 6s 7s and 4f⁷5d³ configurations to low even levels of 4f⁸6s² and 4f⁷6s²6p configurations. Electronic configurations of the energy levels have been discussed on the basis of observed isotope shifts. In some cases assigned configurations have been revised and probable configurations have been suggested.