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Keywords:

Science & Technology, Physical Sciences, Chemistry, Physical, Physics, Atomic, Molecular & Chemical, Chemistry, Physics, CHROMIUM-OXIDE CLUSTERS, ELECTRONIC-STRUCTURE, BASIS-SETS, GAS-PHASE, SPECTROSCOPY, ATOMS, APPROXIMATION, TRANSITIONS, STATES, N=1-5, 0307 Theoretical and Computational Chemistry, 0601 Biochemistry and Cell Biology, 0803 Computer Software, Chemical Physics, 3406 Physical chemistry, 3407 Theoretical and computational chemistry

Abstract:

Geometrical and electronic structures of the chromium oxide dimer in both charge states Cr2O2-/0 were carefully and thoroughly studied using the restricted active space RASSCF/RASPT2 and density matrix renormalization group followed by second-order perturbation theory DMRG-CASPT2 methods in conjunction with large basis sets. The anionic and neutral clusters Cr2O2-/0 are characterized by a D2 h structure and high-spin ground states (10 and 9, respectively). RASSCF wave functions point out strong multireference characters of their electronic ground state. The two lowest-lying states 10Ag and 10B2g of the anion Cr2O2- are nearly degenerate, and both were proven to be populated and involved in the anion photoelectron spectra of Cr2O2-. The neutral cluster exhibits a 9B2g ground state. Within the active space of 20 electrons in 18 orbitals used, 30 electronic transitions starting from both lower-lying anionic states to corresponding neutral states were predicted. Transitions from the anionic ground state 10Ag cause most of visible bands in the anion photoelectron spectra of Cr2O2-, while the first band with low intensity is determined to arise from a transition starting from the nearly degenerate state 10B2g. Furthermore, multidimensional Franck-Condon factor simulations were carried out to further support our band assignments.