Ab initio electronic structure calculations are performed on ethyl adsorbed
on Pt(100) to investigate whether photoexcitation and the resulting electr
on attachment to ethyl will induce dissociation by H transfer to the surfac
e. Calculations are carried out using an embedded cluster description of th
e adsorbate-metal system, and excited electronic states are resolved by con
figuration interaction theory. The results show there is no barrier to H tr
ansfer in the excited state, thereby predicting that ethylene will be forme
d if the excited state has sufficient lifetime.