ELECTRON-ENERGY-LOSS SPECTROSCOPY AND THEORETICAL-STUDY OF TRIPLET AND SINGLET EXCITED-STATES OF FULVENE

Triplet and singlet excited states of fulvene and 6,6'-dimethylfulvene were studied in the gas phase by electron-energy-loss spectroscopy. T wo valence triplet states were observed for each compound, with vertic al transition energies of 2.35 and 3.10 eV for fulvene and 2.35 and 3. 00 eV for 6,6'-dimethylfulvene. The states are assigned as B-3(2) and (3)A(1). The B-1(2) and (1)A(1) valence singlet states and two Rydberg bands, known from photoabsorption spectroscopy, were also observed. T o support the assignments multiconfigurational second-order perturbati on calculations (CASSCF/CASPT2) were performed. The calculated energie s of the first two valence triplet and singlet transitions are within 0.19 eV of the experiment.