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 X7.5 ground state may be described as Dy+[(4f)(9)(6s)(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+[(4f)(10)(6s)(1)]Cl-. The dominant configuration of Dy+[(4f)(9)(6s)(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 (omega(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 [(4f)(10)(6s)(1)], and the A[16.4]8.5 and B[15.4]Omega states observed both have (4f)(10)([6p(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 Omega value.) The Omega value of the B[15.4]Omega state, which has not been determined experimentally, is calculated to be 6.5.