Pyrene Adsorption on a Ag(111) Surface

This work describes the adsorption of pyrene molecules on a Ag(111) surface. We first demonstrate that despite its high vapor pressure, pyrene molecules can form ordered films under ultrahigh vacuum conditions, presenting a well-contrasted diffraction pattern. Studies using high-resolution electron energy loss spectroscopy and ultraviolet photoelectron spectroscopy provide compelling evidence of a physisorbed system where the molecules only weakly interact with the substrate underneath. Comparisons with theoretical calculations, as well as with data obtained from optical spectroscopies, clearly demonstrate that the vibrational and electronic properties of the adsorbed molecules are similar to the expected ones for pristine pyrene. Finally, we used temperature-programmed X-rays photoelectron spectroscopy to study the desorption process of pyrene on the Ag(111) surface and estimate its activation energy to desorption.