13C-Formate as an indirect low-temperature 1H lineshape polarimeter

Abstract

¹H polarization quantification is important for dissolution-dynamic nuclear polarization (dDNP) but can be cumbersome due to the requirement of acquiring thermal equilibrium signals and measurements that are complicated by large background signals. ¹H nuclear magnetic resonance (NMR) spectra can also be deleteriously influenced by line distortions linked with radiation damping from ¹H DNP and cannot be used for accurate calculation of ¹H polarization. Determining ¹H polarization via immediate ¹³C lineshape analysis of a simple molecule removes such complications. We present ¹³C-sodium formate as a straightforward system for indirect ¹H polarimetry. The ¹³C NMR spectra acquired under dDNP conditions have distinct features that are readily reproduced with ¹³C lineshape simulations. ¹H polarizations built-up during ¹H DNP were indirectly inferred by fitting simulations to ¹³C lineshapes. We provide the MATLAB scripts used for ¹³C lineshape analysis in order that the method can be readily implemented in other laboratories.