Photoyield enhancement from small metal particles

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Abstract
The screened electromagnetic field is calculated for light incident on a jellium sphere; this is then used to calculate the photoemission from spheres of radius 20-30 au, using initial and final state wavefunctions appropriate to a square-well potential. The probability of photoemission is enhanced by a factor of about 100 around the Mie plasmon frequency compared with emission from a plane surface, an important contribution coming from resonances in the final state wavefunctions at low energies. The photoemission from an Ag sphere of radius 25 au is also calculated, using the bulk dielectric properties to find the screened electromagnetic field, and free-electron-like initial and final states. As the Mie frequency is well below the threshold for Ag, the photoyield is enhanced by a factor of only 5, and much smaller than the experimentally observed enhancement.