Authentication and testing of banknotes using laser multiphoton electron extraction spectroscopy (MEES)

Abstract

In laser multiphoton electron extraction spectroscopy (MEES), the photo-charges extracted from a surface by a pulsed laser beam are recorded as a function of laser wavelength. We report the first application of this spectroscopy to banknotes. Various banknotes from different countries, authentic and counterfeit, have been tested. The results indicate that MEES spectra are both infor-mative (many peaks) and reproducible. The spectra allow for clear distinction between authentic and counterfeit banknotes. Actually, MEES provides a unique fingerprint of the banknotes, so that distinction between various forgery methods (printer used) is also possible.