Momentum Distribution of Electrons Emitted from Resonantly Excited Individual Gold Nanorods.

Electron emission by femtosecond laser pulses from individual Au nanorods is studied with a time-of-flight momentum resolving photoemission electron microscope (ToF k-PEEM). The Au nanorods adhere to a transparent indium–tin oxide substrate, allowing for illumination from the rear side at normal incidence. Localized plasmon polaritons are resonantly excited at 800 nm with 100 fs long pulses. The momentum distribution of emitted electrons reveals two distinct emission mechanisms: a coherent multiphoton photoemission process from the optically heated electron gas leads to an isotropic emission distribution. In contrast, an additional emission process resulting from the optical field enhanceme…