Polarisation dynamique nucléaire à haut champ magnétique et résonance paramagnétique électronique

Abstract

This article relates two recently developed magnetic spectroscopy methods. Both methods use the electron magnetic moment, which is significantly more intense than the more commonly used nuclear magnetic moment. This is because, at a given temperature and magnetic field, electrons are much more strongly polarised than nuclei. This property is used in dynamic nuclear polarisation (DNP) to increase the sensitivity of nuclear spin detection by several orders of magnitude. This article first describes how the recent development of high-frequency microwave sources and DNP probes compatible with pneumatic rotation of the sample ("magic angle spinning") have extended this hyperpolarisation technique to the most intense magnetic fields currently available (> 10 tesla). The second part shows how a strong electron magnetic moment allows to measure long distances in disordered systems by pulsed electron paramagnetic resonance. By measuring the dipolar interaction between two electron spins, using a sequence known as DEER, it becomes possible to measure distances up to 80 Å in disordered systems. This technique has many applications in chemistry and biology.