The Rydberg states of trans-butadiene from generalized valence bond and configuration interaction calculations

Self-consistent ab initio generalized valence bond (GVB) and configuration interaction (CI) calculations are presented for the Rydberg states of trans-1,3-butadiene. Five Rydberg series were identified, three optically allowed (np_z,, np_x and (nf_x)³) and two optically forbidden (ns and (nd_z)²). It is shown that, except for the à and F bands (which correspond to the non-valence 1 ¹Bu and the valence 2 ¹A, states, respectively) all the transitions observed in the ultra-violet (UV) and electron-impact (EI) spectra, and in the two-photon spectra, can be assigned to members of these Rydberg series.