The ionized states of 6,6-dimethylfulvene; the vibrational energy levels studied by photoionization, configuration interaction and density functional calculations

A new synchrotron-based photoionization spectrum of 6,6-dimethylfulvene shows significant vibrational fine structure (VFS), in contrast to previous studies; this was successfully analysed by Franck-Condon (FC) methods. The sequence ionic states the range 7 19 eV has been determined both symmetry adapted cluster configuration interaction and density functional methods, especially using long-range corrected version Becke three-parameter hybrid (B3LYP) Coulomb-attenuating method (CAM-B3LYP). Both lead reliable theoretical values for calculated vertical adiabatic ionization energies. FC profile lowest energy (IE1, X2A2) extensive VFS which is successfully. second IE (A2B1) truncated owing overlap with IE1.