title: Role of the Substrate Orientation in the Photoinduced Electron Dynamics at the Porphyrin/Ag Interface.
abstract: Photochemically activated reactions, despite being a powerful tool to covalently stabilize self-organized molecular structures on metallic surfaces, have struggled to take off due to several not yet well understood light-driven processes that can affect the final result. A thorough understanding of the photoinduced charge transfer mechanisms at the organic/metal interface would pave the way to controlling these processes and to developing on-surface photochemistry. Here, by time-resolved two-photon photoemission measurements, we track the relaxation processes of the first two excited molecular states at the interface between porphyrin, the essential chromophore in chlorophyll, and two different orientations of the silver surface. Due to the energy alignment of the porphyrin first excited state with the unoccupied sp-bands, an indirect charge transfer path, from the substrate to the molecule, opens in porphyrin/Ag(100) 250 fs after the laser pump excitation. The same time-resolved measurements carried out on porphyrin/Ag(111) show that in the latter case such an indirect path is not viable.
authors.affiliation: I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Tognolini
authors.affiliation: I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ponzoni
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova and Consorzio INSTM , Via Marzolo 1, 35131 Padova, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sedona
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova and Consorzio INSTM , Via Marzolo 1, 35131 Padova, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Sambi
authors.affiliation: I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Pagliara
keywords: Organic/metal interface; charge transfer; hot electrons; time-resolved photoemission