Abstract
The time‐resolved two‐photon photoemission technique (TR‐2PPE) has been applied to study static and dynamic properties of localized surface plasmons (LSP) in silver nanoparticles. Laterally, integrated measurements show the difference between LSP excitation and nonresonant single electron‐hole pair creation. Studies below the optical diffraction limit were performed with the detection method of time‐resolved photoemission electron microscopy (TR‐PEEM). This microscopy technique with a resolution down to 40 nm enables a systematic study of retardation effects across single nanoparticles. In addition, as will be shown in this paper, it is a highly sensitive sensor for coupling effects between nanoparticles.
Highlights
The interaction of light with metal nanoparticles has attracted considerable attention for many centuries
Since plasmons are associated with large electromagnetic fields near the particle surface, they play an important role in surface-enhanced Raman scattering (SERS) [12], second harmonic generation [13, 14], and multiphoton photoemission [15,16,17,18,19]
We show that 2PPE in combination with the photoemission electron microscopy technique (PEEM) allows to map local near field variations associated with plasmonic excitations with subdiffraction (
Summary
The interaction of light with metal nanoparticles has attracted considerable attention for many centuries. During the last decades, lots of theoretical studies focused on the properties of LSP in nanostructures of different shapes in order to gain insight, for example, into their optical response, the field distribution of the resonant modes as well as relevant decay channels, and the coupling between neighbouring particles [21,22,23]. The induced polarizations of these different, coherently coupled transitions superpose to a macroscopic polarization which represents the collective response of the electronic system This induced polarization field adds to the incident light field and causes a modification of the particle internal field (Figure 1). The decay of a plasmon is possible by the creation of electron-hole pairs and a subsequent transfer of energy to the internal degrees of freedom inside the particles (internal damping) This process results in a complete loss of coherence to the exciting light field. Observed effects that will be discussed are the field retardation in large nanoparticles and the plasmongoverned coupling of neighbouring nanoparticles
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