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

Abstract

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 (ωe) 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]Ω states observed both have (4f)10([6p1/2,1/2])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.