Microwave-Free Nuclear Spin Hyperpolarization through Photo-CIDNP in Static and Rotating Solids

This study advances the theoretical foundation of photo-chemically induced dynamic nuclear polarization (photo- CIDNP)-a powerful mechanism for enhancing nuclear spin sensitivity without microwave irradiation. Using an operator-based effective Hamiltonian approach, we derive precise resonance matching conditions and identify key dipolar scaling factors governing the photo-CIDNP Hamiltonian under both static and magic-angle spinning (MAS) conditions. Our analytical formulation of coherent evolution of photoexcited singlet state exhibits strong agreement with numerical simulations, reinforcing the validity of our theoretical framework. By unraveling the intricate interplay of spin parameters in the radical-pair mechanism, our findings provide critical insights for optimizing photo-CIDNP efficiency and guiding the rational design of tailored molecular systems. The ability to develop highly efficient photo- CIDNP sensitizers marks a crucial step toward harnessing hyperpolarized NMR and MRI, paving the way for next- generation advancements in biomedical imaging and materials science