Centre National De La Recherche Scientifique

Thomson-csf

Patrick Batail

Philippe Robin

Denis Jerome

Albert Robert

Georges Tevanian

Francoise Bertho

Marc Fourmigue

The invention relates to a method of authenticating an object by electron paramagnetic resonance spectroscopy, the method being characterized in that at least one authenticating substance is added to the object, said substance having an EPR peak whose width is not greater than about 1.5 gauss, with the spectroscopy being performed in a static field of an amplitude such that the substance has a resonance frequency in the radio-frequency domain, and with the width of the EPR peak of the substance being used as a criterion for discrimination. The static field preferably has a low frequency colinear modulation field superposed thereon having an amplitude which is substantially greater than the EPR width of the substance, and under a radiofrequency electromagnetic field extending perpendicularly to the static field and to the modulation field and having an amplitude which is not less than the peak width, whereby paramagnetic materials having a peak width which is greater than that of the authenticating substance are not detected. The invention also provides apparatus for implementing the method, and security paper useable with the method.

Method of authenticating an object by electron paramagnetic resonance,

The invention pertains to organic compounds of the tetrahiafulvalene type made amphiphillic by substitution of the radicals R.sup.1 and R.sup.2 meeting one of the following conditions:

Organic compounds of the tetrathiafluvalene type which can be used to

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Paris, France

Patrick Batail