Abstract
The partially filled 4f shell in rare earths gives rise to complex multiplet structure in both photoelectron spectroscopy (PES) and bremsstrahlung isochromat spectroscopy (BIS). The fractional parentage theory previously applied to PES is extended to BIS, and a similarity is predicted between the PES of a 4fn element and the BIS of a 4f14-n element. Fractional parentage arguments are also applied to the linewidths of the 4f multiplet levels as observed in electron spectroscopy.