Enhancement of the Infrared Absorption from Molecular Monolayers with Thin Metal Overlayers

The infrared absorption from molecular monolayers is enhanced a factor of 20 by thin metal overlayers or underlayers with use of the attenuated-total-reflection technique. The total enhancement, including contributions from the attenuated-total-reflection geometry, is almost ${10}^{4}$. This effect is consistent with an electric field enhancement due to collective electron resonances associated with the island nature of the thin metal films.