The vibrational excitation in the energy ranges of the lowest resonances in benzene has been measured and it is found that only few fundamental modes become excited. This selectivity of the excitation process can be understood in terms of selection rules which are based on symmetry considerations. The angular distribution of scattered electrons in the range of the lowest shape resonance (∼1.2 eV) is consistent with an $f_{\delta }$ wave as the dominant partial wave.

• Received 28 August 1975

DOI:https://doi.org/10.1103/PhysRevLett.35.1429