Fig. 1.

Excited states of thymine and their electronic characters. a Isosurface representations (right) and electron density projections onto the molecular plane for the three valence orbitals (Hartree–Fock/6-311 G) involved in the characters of the two lowest lying excited states of thymine and a core orbital localized at oxygen(8). The electron density at the position of the core orbital differs strongly for the different valence orbitals. b Results from our coupled cluster investigation of the excited-state topology along the two most relevant degrees of freedom for relaxation into the nπ* minimum. All states are labeled with their electron configuration. Ultraviolet (UV) excitation of the ground state (GS) places a nuclear wavepacket (gray) on the ππ* excited state. It relaxes through a conical intersection to a minimum in the nπ* excited state. According to our calculations, only one core-excited state (CE) characterized by an excitation at O(8) is relevant for interpretation of our experimental results