Theoretical interpretation of the photoelectron spectra of Al3O2- and Al3O3-

Hartree-Fock (KF) and density functional theory (DFT) calculations have been used to determine the equilibrium geometries of the ground electronic state of Al3O2, Al3O3, and their corresponding negative ions. The calculated global minimum for Al3O2 has a "vee" shape of C-2v symmetry with a (a(1))(1.2)A(1) configuration. A kite-shaped structure of C-2v symmetry has been obtained as a local minimum with a (b(2))B-1 2(2) configuration. The corresponding negative ions have also been found to be global and local minima, respectively, with (a(1))(2) (1)A(1) and (b(2))(2 1)A(1) electron configurations. A higher energy trigonal bipyramidal D-3h structure has been found with a (1)A(1)' (e')(4) electron configuration. For Al3O3-, the calculated global minimum has a bicyclic rectangular shape of C-2v symmetry with a (b(2))(2 1)A(1) configuration, whereas the corresponding neutral Al3O3 with a (b(2))B-1 2(2) configuration has been found to be a local minimum. On the other hand, a kite shape of C-2v symmetry with a (a(1))(1 2)A(1) configuration has been found to be the global minimum of neutral Al3O3. The lowest tripler state of Al3O3- had a hexagonal shape of D-3h symmetry with a (e')(2) configuration. This triplet minimum has slightly higher energy than either of the singlet minima. Configuration interaction (CI) calculations have been performed using the DFT optimized geometries for the two lowest energy structures of Al3O2- and the two lowest energy structures of Al3O3- to determine the low lying vertical excited states of Al3O2 and Al3O3 Those results have been utilized to interpret the recently reported experimental photoelectron spectra of Al3O2- and Al3O3- On the basis of the present CI results, the symmetry of the states involved in the photoelectron peaks have been assigned for both spectra.