Surface-induced changes of the optical response of particles in nanoscaled layered systems: a combined experimental and theoretical study

摘要

Abstract: In this work we study metal surface-induced changes of lifetime and transition frequency of alkali atoms and clusters, deposited onto nanoscaled insulator-metal systems. The systems are made of rough metallic surfaces (characterized by atomic force microscopy), onto which ultrathin organic films as spacer layers (characterized by LEED) are epitaxially grown. We observe an unusually small red shift of the transition frequency of Na atoms of a few hundred Megahertz, which is due to the interaction with the metal surface. This is explained by the nonlocal response of the surface, i.e., the excitation of multipole surface plasmons (MSPs) in the selvedge region of the metal surface, which is influenced by surface roughness. The MSPs should become observable also via linear optical methods such as attenuated total reflection spectroscopy. As a first step in this direction, we present linear extinction spectra of alkali cluster films that are grown on top of organic spectra layers of different length. Due to the interaction with the gold films a red shift of the dipole plasmon resonance is observed, which increases with decreasing chain length.!34