  This paper presents modelled results for optical absorption in ultra-thin
films of nickel, gold and silver across the solar spectrum. It is found in the
case of nickel there is an optimum thickness for maximum solar absorption
around 10-13nm. It is believed that this is a result of the real and imaginary
parts of its refractive index being of similar magnitude across the solar
spectrum which can give rise to very strong thin film absorption.
