Surface amplification of photoionization signal

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Abstract
A new effect involving the interaction of electromagnetic radiation with adsorbed molecules is presented. A long pulsed, low peak power laser has been used in order to induce ionization of several organic compounds adsorbed on thin metal films. An enhancement in the electron signal of several orders of magnitude is observed, as compared to conventional gas phase multiphoton ionization. Two experimental configurations have been used. The surfaces were illuminated either through external or internal reflection. In this study the ionization spectra of molecules on surfaces is presented and the mechanism is discussed. It is believed that this effect relies upon the production of positive ions on the metal surface which lowers the work function sufficiently to allow efficient generation of photoelectrons by the photon flux.

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