title: Ionization-Induced Structural Changes in Uracil Dimers and Their Spectroscopic Signatures.
abstract: The electronic structure of the three representative isomers of the ionized uracil dimers is characterized by high-level electronic structure calculations. Noncovalent interactions between the fragments lower the vertical ionization energies by 0.13-0.35 eV, the largest drop being observed for the stacked and the T-shaped isomers. The initial hole is delocalized in the stacked and the H-bonded isomers and is localized in the T-shaped one. The ionization induces significant structural relaxation and increases the binding energies. The stacked dimer cation relaxes to the symmetric structure bound by 22.7 kcal/mol. The T-shaped dimer cation has a binding energy of 25.1 kcal/mol. Thus, the relative order of the stacked and T-shaped isomers is reversed upon ionization. Finally, the H-bonded isomer, which relaxes to the proton-transferred structure, is bound by 37.0 kcal/mol. The electronic spectra of all three isomers characterized at the vertical and the relaxed geometries show different patterns, which may be exploited in spectroscopic probing of ionization-induced dynamics in these species.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Zadorozhnaya
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482.
authors.forename: Anna I
authors.initials: AI
authors.lastname: Krylov