A study of the excited states in cytosine and guanine stacks in the Hartree-Fock and exciton approximations.

We report calculated exciton energies for the cytosine and guanine stacks obtained in the ab initio Hartree-Fock crystal orbital and exciton approximation, which includes the excited electron-hole interaction. This interaction plays an important role in the description of excited electron spectra in the low-energy region. The stacks were chosen as examples of polymers with helical symmetry.