Spectrum and energy levels of five-times-ionized rhenium

Spectra of Re vi were produced with sliding-spark and triggered-spark discharges. They were recorded photographically with 10.7-m grazing-incidence and normal-incidence spectrographs and with a 3-m normal-incidence spectrograph. Energy levels of the 5d2, 5d6s, 5d6p, 6s6p, and 5d5f configurations were determined with 121 classified lines. Previously no levels were known. Radial parameters were fitted to the energy levels and used for predicting the missing levels and for determining the eigenvector compositions. The onset of collapse of the 5f orbit caused a noticeable term dependence of the expectation value of the orbital radius 〈r〉.