The 3d8-(3d74p + 3p53d9) transitions in Br X: A striking case of configuration interaction

The spectrum of nine times ionized bromine (Br X) was photographed in the 90-120 A wavelength region on a variety of grazing incidence spectrographs using an open spark and a triggered spark as light sources. The analysis of the 3d8-(3d74p + 3p53d9) transitions has resulted in establishing all 9 levels of the 3d8 configuration, all 12 levels of the 3p53d9 configuration and 99 out of 110 levels of the 3d74p configuration. The excitation probability of the 3p inner-shell electron increases with nuclear charge and in Br X is comparable with the excitation probability of the optical electrons resulting in a very strong configuration interaction between the 3p53d9 and 3d74p configurations. Parametric calculations treating these configurations as one super configuration support the analysis. Two hundred and thirty two lines have been classified in this spectrum. (orig.)