Low Frequency Electron Paramagnetic Resonance Spectroscopy
Electron paramagnetic resonance (EPR) spectroscopy can be used to analyze paramagnetic substances, that is, substances with one or more unpaired electrons. Electrons have two different energy configurations, or levels, when placed in an external magnetic field. The electronic energy difference between the two levels is different for each substance the electrons are in. By sending fixed frequency photons into the sample and sweeping the magnetic field, researchers can record a spectrum for each substance.
Conventional EPR spectrometers operate at 9 GHz and tend to be destructive to the sample. On the other hand, an EPR spectrometer operating at a lower frequency (441 MHz) can be nondestructive, but very little work has been done on these instruments. Therefore, we have created a library/database of LFEPR spectra for common pigments used in paintings. Pigments, even ones with similar optical properties that are hard to distinguish from each other by traditional methods, possess unique EPR spectra that can be used to identify them. Since the database also includes information about the history of each pigment, it can be of use to museum curators, art collectors, and historians to determine the authenticity and the age of a painting.