The fourth spectrum of rhenium (Re IV): Determination of the 5d4, 5d36s and 5d36p configurations

The spectrum of rhenium was observed in the (500-2100) Å wavelength region. The (5d4 + 5d36s) − 5d36p transition array of three times ionized rhenium, Re IV, has been investigated and 975 spectral lines have been classified in the region of (786-2063) Å. The analysis has led to the determination of the 5d4, 5d36s and 5d36p configurations. Thirty two of 34 theoretically possible 5d4 levels, 33 of 38 possible 5d36s levels and 95 of 110 possible 5d36p levels have been established. The orthogonal operators technique was used to calculate the level structure and transition probabilities. The energy parameters have been determined by the least squares fit to the observed levels. Calculated transition probability and energy values, as well as LS-compositions obtained from the fitted parameters are presented.