ABINITIO PSEUDOPOTENTIAL STUDY OF YBH AND YBF

SCF and large scale MRCI calculations using quasi-relativistic energy-adjusted ab initio pseudopotentials for Yb treating the 4f orbitals explicitly in the valence space together with extended basis sets have been performed for low-lying electronic states of YbH and YbF in the LAMBDA-S-coupling scheme. Spin-orbit coupling was treated by means of energy-adjusted ab initio spin-orbit operators in connection with quasi-relativistic DGCI calculations in the intermediate coupling scheme. The results for the YbH 4f14-sigma-2-sigma-1 2-SIGMA+ (OMEGA = 1/2) and YbF 4f14-sigma-2-sigma-pi-4-sigma-1 2-SIGMA+ (OMEGA = 1/2) ground states (YbH: R(e) = 2.074 angstrom, D0 = 1.43 eV, omega(e) = 1276 cm-1, YbF: R(e) = 2.045 angstrom, D0 = 4.87 eV, omega(e) = 492 cm-1) are in excellent agreement with available experimental data (YbH: R(e) = 2.053 angstrom, D0 less-than-or-equal-to 1.93 eV or less-than-or-equal-to 1.55 eV, omega(e) = 1249 cm-1; YbF: R(e) = 2.016 angstrom, D0 = 4.80 eV or > 5.36 eV, omega(e) = 502 cm-1). A combination of inexpensive pseudopotential molecular orbital calculations including the 4f orbitals in the pseudopotential core and subsequent ligand field calculations for the 4f shell is proposed and shown to yield results in satisfactory agreement with those of higher level calculations.