Electron scattering in ethene: Excitation of the ã 3B1u state, elastic scattering, and vibrational excitation

Experimental and calculated absolute differential cross sections for the scattering of low-energy electrons from ethene are presented. Emphasis is on the excitation of the ã 3B1u 3(pi,pi*) state, but selected elastic and vibrational excitation cross sections are also given. In contrast to earlier calculations, which were nearly a factor of 2 too large, the present calculation agrees very well with the experimental triplet excitation cross section in the threshold region. The improvement is due primarily to the inclusion of target polarization, which results in proper positioning of the pi* resonance, whose high-energy tail dominates the triplet state excitation near threshold. The present experimental elastic cross sections agree very well with recent calculations taking into account target polarization.