The presentation will explore the potential applications of two new magnetic resonance techniques to cultural heritage science. The new techniques enable a minimally invasive/non-invasive observation of magnetic resonance spectra and thus are promising new tools for the structure characterization of art and archaeological materials at the molecular level. The first technique, dynamic nuclear polarization (DNP), is a recently developed method that can enhance the sensitivity of solid state NMR spectroscopy by 1-3 orders of magnitude. It is well suited to the NMR study of surfaces, minority phases in mixtures, and cases where only limited sample quantities are available. Such challenges are often encountered in the characterization of cultural heritage materials. We have combined DNP with two other recent solid state NMR techniques to demonstrate the feasibility of DNP-enhanced ultra-wideline NMR. We have detected the 207Pb NMR spectrum of lead palmitate with high sensitivity by this method. Using DNP-enhanced ultra-wideline NMR we have also observed the first 207Pb NMR spectrum of the pigment basic lead white (hydrocerussite). With this technique we can probe the reactivity of hydrocerussite and the mechanism of lead soap formation implicated in the deterioration of oil paintings. Electron paramagnetic resonance (EPR), which detects free radicals and other paramagnetic species such as transition metal ions, is an established archaeometric technique. Conventional EPR however is an invasive method that requires substantial sample removal. The second technique we introduce is low frequency EPR (LFEPR), a novel technique that allows the completely non-invasive observation of EPR spectra at multiple locations on intact objects. We shall discuss the opportunities and challenges of LFEPR and show survey spectra from ceramic objects and marble. We shall illustrate the technique in detail by analyzing the LFEPR spectra of structural Fe (III) in kaolin as a function of firing temperature. Particle-size-dependent signals from Fe(III) oxides in superparamagnetic domains, and ferromagnetic resonance effects from stoneware fired at high temperatures have also been detected.

Exploring the potential of advanced magnetic resonance techniques for the characterization of cultural heritage materials

251st National Meeting (2016)

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