[en] The electron-beam ion trap at Lawrence Livermore National Laboratory is used to excite levels selectively in lithiumlike Cr21+, Mn22+, Fe23+, Ni25+, and Ge29+ that possess two radiative-decay branches in the x-ray regime. High-resolution spectroscopic measurements of the relative x-ray intensities are made to infer the radiative branching ratio. Results are compared with theoretical values and demonstrate the importance of relativity in the determination of level structure and mixing coefficients in configuration-interaction calculations