An electron impact investigation of the forbidden and allowed transitions of norbornadiene

In this electron impact investigation of the excited states of norbornadiene, variable scattering angle and incident energy have been employed to distinguish between different types of electronic transitions. Rydberg transitions have been observed to the first and second ionization limits. Forbidden valence transitions have been observed at 5.25 and 7.50 eV and allowed valence transitions at 5.95 and 6.65 eV. Based on the electron impact energy loss spectrum, the splitting of the occupied orbitals is estimated to be 0.95 eV and that of the excited states is 1.3 eV. Either little or constant electron rearrangement appears to accompany electron promotion. The unperturbed transition energy is estimated to be approximately equal to that observed for norbornene.