Ionization energies and Dyson orbitals of thymine and other methylated uracils

Electron propagator methods are applied to the calculation of photoelectron spectra of thymine and other C- and N-methylated uracils. The Partial Third-Order electron propagator method is used. Excellent agreement with existing experimental spectra is achieved. Relationships between reductions in ionization energies and antibonding contributions from methyl groups in corresponding Dyson orbitals are discussed.