Discrete dipole approximation for low-energy photoelectron emission from NaCl nanoparticles

This work presents a model for the photoemission of electrons from sodium chloride nanoparticles 50-500 nm in size, illuminated by vacuum ultraviolet light with energy ranging from 9.4 to 10.9 eV. The discrete dipole approximation is used to calculate the electromagnetic field inside the particles, from which the two-dimensional angular distribution of emitted electrons is simulated. The emission is found to favor the particle's geometrically illuminated side, and this asymmetry is compared to previous measurements performed at the Lawrence Berkeley National Laboratory. By modeling the nanoparticles as spheres, the Berkeley group is able to semi-quantitatively account for the observed asymmetry. Here however, the particles are modeled as cubes, which are closer to their actual shape, and the interaction of an emitted electron with the particle surface is also considered. The end result shows that the modeled emission asymmetry for these low-energy electrons is more sensitive to the interaction with the particle-surface than to the specific particle shape, i.e., a sphere or cube. (C) 2011 Elsevier Ltd. All rights reserved.