Leavesley, Alisa, Ilia Kaminker, and Songi Han. “Versatile Dynamic Nuclear Polarization Hardware with Integrated Electron Paramagnetic Resonance Capabilities,” 7:22, 2018.
https://doi.org/10.1002/9780470034590.emrstm1564.
Successful application of dynamic nuclear polarization (DNP) often relies on procedures and sample formulations that are empirically optimized. In order to expand the scope of DNP to a wider range of sample systems and applications, a better understanding of the underlying DNP mechanism and spin dynamics is required. An aspect of DNP spin dynamics that is understudied is the electron spins, which can be attributed to high-field EPR capabilities not being commonly available under DNP conditions. Here, we present a combined and versatile DNP/EPR instrument that allows us to simultaneously follow the electron and nuclear spin dynamics during the course of the DNP experiment. A modular design ensures the versatility of such an instrument, where a solid-state microwave (μw) source permits high agility for electron spin manipulation. This article presents a detailed description of the DNP/EPR instrument, including the discussion of the components required for a dual DNP/EPR instrument, the integration of arbitrary waveform generation for shape μw pulses, and a two-source quasi-optical configuration that enables artifact-free electron–electron double resonance experiments at 200 GHz. We conclude by providing select examples in which the evaluation of electron spin dynamics was necessary to elucidate the underlying DNP mechanism.