Ground and low-lying excited states of DyCl studied by the four-component relativistic configuration interaction methods

The ground and low-lying excited states of the DyCl molecule are investigated by the four-component relativistic CI methods. Electronic states are classified into so-called families by applying the f -shell Omega decomposition method to the CI wavefunctions, and the characters of the states are clarified. The X 7.5 ground state may be described as Dy + [(4 f ) 9 (6 s ) 2 ]Cl − , but at large nuclear distance ( R > 4.80 au), beyond the equilibrium nuclear distance (4.724 au), the dominant configuration changes to Dy + [(4 f ) 10 (6 s ) 1 ]Cl − . The dominant configuration of Dy + [(4 f ) 9 (6 s ) 2 ]F − is retained in DyF, but the dominant configuration in DyCl changes drastically as R increases. The calculated value (231 cm −1 ) of the vibrational frequency ( ω e ) agrees well with the value of 233 cm −1 observed by Linton et al. (J Mol Spectrosc 232:30–39, 2005 ). This low frequency reflects the weakness of the Cl − ligand compared to F − . The Y [0.15]8.5, Z [0.85]7.5, and [0.97] states observed by Linton et al. are found to have a dominant configuration of [(4 f ) 10 (6 s ) 1 ], and the A [16.4]8.5 and B [15.4]Ω states observed both have (4 f ) 10 ([6 p 1/2,1/2 ]) 1 , belonging to different families. (The number in square brackets denotes the excitation energy in unit of k cm −1 , and the number after a right square bracket denotes an Ω value.) The Ω value of the B [15.4] Ω state, which has not been determined experimentally, is calculated to be 6.5.