From proton to deuteron relaxometry: The next generation of field-cycling NMR relaxometers

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By applying the field-cycling (FC) technique, NMR relaxometry has made a big step forward providing access to the frequency dependence of the spin-lattice relaxation in all kinds of soft matter. The frequency dependence directly reflects the molecular dynamics. Most FC studies focus on protons. Due to the multi-particle character of the relevant interaction a super-position of molecular reorientation and translation is probed, which often hampers quantitative insights. In contrast, deuteron FC NMR solely detects reorientation and, hence, theoretical understanding and computer simulation are strongly facilitated. One also profits from the isotope selectivity of NMR which allows data to be interpreted in a much more specific way as compared to other methods. However, as the deuteron NMR frequency is small, current FC relaxometers are not suitable for routine FC NMR studies. Rather, a new generation of relaxometers has to be developed. A combination of quickly switching thousands of amperes in a sophistically designed coil system and reaching a strong magnetic field of high accuracy make the task very demanding. It is the aim of the present project to achieve this and to make deuteron FC NMR a routine technique of “molecular rheology”. Likewise, investigations of other nuclei such as 7Li, 13C, and 31P will become possible, and even proton relaxometry will strongly benefit.