High energy photoelectron emission from gases using plasmonic enhanced near-fields

We study theoretically photoelectron emission in noble gases using plasmonic enhanced near-fields. We demonstrate that these fields have a great potential to generate high energy electrons by direct excitation from mid-infrared laser pulses of current femtosecond oscillators. Typically, these fields appear in the surroundings of plasmonic nanostructures with various geometrical shapes, such as bow-ties, metallic waveguides, metal nanoparticles and nanotips, when illuminated by a short laser pulse. Here, we consider metal nanospheres, in which the spatial decay of the near-field of the isolated nanoparticle can be approximated by an exponential function according to recent attosecond streaking measurements. We establish that the strong spatial inhomogeneous character of the enhanced near-field plays an important role in the above threshold ionization (ATI) process and leads to a significant extension in the photoelectron spectra. In this work, we employ the one-dimensional time-dependent Schrodinger equation to calculate the photoelectron emission of xenon atoms in such enhanced near-fields. Our findings are supported by classical calculations.