title: Efficient strategies for accurate calculations of electronic excitation and ionization energies: theory and application to the dehydro-m-xylylene anion.
abstract: In the dehydro-m-xylylene (DMX) anion [Munsch; et al. J. Org. Chem. 2004, 69, 5735], three nearly degenerate orbitals host four electrons, which results in a large number of nearly-degenerate electronic states. By using this challenging example, we assess the performance of the multireference "brute force" approach and the two-step schemes based on single-reference methods for calculating accurate energy differences. Different schemes for calculating adiabatic ionization potential (IP) of DMX- are also investigated. IP calculated by single-reference based schemes is in excellent agreement with experiment.
authors.affiliation: Department of Chemistry, University of Southern California, SSC 409A, Los Angeles, California 90089-0482, USA.
authors.forename: Lyudmila V
authors.initials: LV
authors.lastname: Slipchenko
authors.forename: Anna I
authors.initials: AI
authors.lastname: Krylov
mesh_terms: D000838:Anions / Q000737:chemistry; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D014992:Xylenes / Q000737:chemistry*
chemical_list: D000838:Anions; D005609:Free Radicals; D014992:Xylenes