“…The symmetric behavior around the Fermi energy corroborates the assumption that both processes are triggered by inelastic electron tunneling. ,, A strong gradient in the electron yield indicates the opening of an additional inelastic tunneling channel, possibly related to the onset of a vibrational mode. , If the energy of the vibrational mode is sufficiently high, tunneling through or lifting above the potential barrier eventually triggers the molecule’s rotation or tautomerization. ,, In order to extract possible vibrational modes, the graphs in Figure a,b were analyzed quantitatively by a spectral fitting method. , The resulting energy onsets are summarized in Table . Negative and positive thresholds are in accordance with the first and second harmonic of the N–H stretching mode, an observation which agrees well with previous results for tautomerization of phthalocyanine on the Ag(111) as well as the Cu(111) surface. , Therefore, we conclude that both processes, tautomerization and rotation, are triggered by the N–H stretching mode.…”