Near-field electron energy loss spectroscopy of nanoparticles

Near-field spectroscopy of nanoparticles was performed with a subnanometer probe size, using a scanning transmission electron microscope. at nonintersecting beam-particle configuration, surface collective modes are isolated from the entire excitation spectrum. The relativistic narrow beam generates a new type of spatial dispersion and may induce an additional spectral quantization. Line intensity variations during the mapping can be accounted for quantitatively by using a relatively simple theoretical model. This method is also suggested as a new way for transmission electron microscopy studies of beam sensitive samples.