Electronic structure and spectrum of UO_2~(2+)and UO_2Cl_4~(2-)

摘要

A theoretical study is presented of the electronic spectra of the UO_2~(2+)and UO_2Cl_4~(2-)ions,based on multiconfigurational perturbation theory(CASSCF/CASPT2),combined with a recently developed method to treat spin-orbit coupling[P.-A.Malmqvist et al,Chem.Phys.Lett.357,230(2002);B.O.Roos and P.-A.Malmqvist,Phys.Chem.Chem.Phys.6,2919(2004)].The results are compared to the experimental spectroscopic data obtained for uranyl ions in Cs_2UO_2Cl_4 crystals from Denning[Struct.Bonding(Berlin)79,215(1992)]and to previous theoretical calculations performed using a combined configuration-interaction spin-orbit treatment[Z.Zhang and R.M.Pitzer,J.Phys.Chem.A 103,6880(1999);S.Matsika and R.M.Pitzer,J.Phys.Chem.A.105,637(2001)].As opposed to the latter results,the calculations performed in this work point to a significant effect of the weakly bound equatorial chlorine ligands on the excitation energies.