[en] Time-and angle-resolved two-photon photoemission (2PPE) is used to probe the dynamics of electrons at model polar molecule/metal interfaces

[en] Two-photon photoemission of image potential states above monolayers of p-xylene/Ag(III) shows that electrons with different momenta have very different rise and decay rates as a function parallel momentum

[en] The thickness-dependent interfacial band structure was determined for thin films of Co(6) on Ag(111) by angle-resolved two-photon photoemission spectroscopy

[en] The ability of time and angle-resolved two photon photoemission to estimate the size distribution of electron localization in the plane of a metal/adsorbate interface is discussed

[en] This manuscript details the observation of electron solvation by a two-dimensional interface

[en] Femtosecond laser excitation has been used to initiate desorption of molecular oxygen from the (111) surface of Pd and to study the adsorption-state dependence of the substrate-adsorbate coupling. The relative populations of the two chemical states, peroxo (O₂^2-) and superoxo (O₂^-), were varied by changing the total coverage. Two-pulse correlation measurements exhibit a dominant 400 fs response and a slower 10 ps decay that are relatively independent of the initial O₂ coverage. In contrast, the photodesorption yield and the nonlinearity of the fluence dependence show a systematic coverage dependence. The coverage-independent subpicosecond response indicates that the photoinduced desorption from the two states is driven primarily by the same electron-mediated mechanism, while the coverage dependence of the yield indicates that the desorption efficiency from the superoxo state is greater than that from the peroxo state. These results are discussed in the context of the electron-phonon two-temperature model with an empirical adsorbate-electron frictional coupling that depends on both the electronic temperature and the activation energy for desorption. With a coupling strength that decreases as the activation energy decreases, the trends with varying coverage, absorbed fluence, and time delay can all be reproduced. The model is consistent with a transition from a resonantly enhanced (diabatic) regime to an adiabatic regime as the system relaxes, accounting for the biexponential correlation behavior