Resonant Mixing Dynamic Nuclear Polarization

We propose a mechanism for dynamic nuclear polarizationthat isdifferent from the well-known Overhauser effect, solid effect, crosseffect, and thermal mixing processes. We term it ResonantMixing (RM), and we show that it arises from the evolutionof the density matrix for a simple electron-nucleus coupledspin pair subject to weak microwave irradiation, the same interactionsas the solid effect. However, the SE is optimal when the microwavefield is off-resonance, whereas RM is optimal when the microwave fieldis on-resonance and involves the mixing of states by the microwavefield together with the electron-nuclear coupling. Finally,we argue that this mechanism is responsible for the observed dispersive-shapedDNP field profile for trityl samples near the electron paramagneticresonance center.