Construction of a liquid-state NMR DNP shuttle spectrometer: First experimental results and evaluation of optimal performance characteristics

Abstract

First results from a liquid-state shuttle dynamic nuclear polarization (DNP) spectrometer are presented. The device polarizes a water sample at 9.7 GHz and 0.34 T in a commercial Bruker electron paramagnetic resonance (EPR) spectrometer and then transfers the sample via a homebuilt pneumatic shuttle device into the 600 MHz and 14.09 T nuclear magnetic resonance (NMR) spectrometer with a conventional NMR probe for detection. The shuttle transfer time is approximately 115 ms. Initial experiments measure the postshuttle proton magnetization compared with the Boltzmann magnetization at 14.09 T. The DNP enhancement factor at 0.34 T is reported for the nitroxide polarizer TEMPOL in water solution. Reduction of the magnetization during shuttling because of relaxation is quantified. Optimization of this apparatus is expected to bring the NMR enhancement factor for protons close to the theoretical enhancement maximum of -7.92.