Relativistic calculations of low-lying electronic states of ruthenium and osmium

Calculations of the ground state and low-lying excited electronic states of Ru I and Os I have been carried out using multireference highly correlated relativistic methods. We calculated 34 lowest even J levels of Os. The root mean square deviations (RMSD) of theoretical values from experiment for the four lowest electronic terms and their J-level splittings were less than 115 and 90 cm−1, respectively, for Ru. The RMSD for the energy levels of the four lowest electronic terms of Os were in the interval 146–442 cm−1 and for level splittings were in the interval 94–478 cm−1.