Surprising Consequences of High Electron Spin Polarization | Dr. Quentin Chappuis Stern | Session 59

During the 59th session of the Global NMR Discussion Meetings held on January 10th, 2023 via Zoom, Dr. Quentin Chappuis Stern gave a talk on the topic "The surprising consequences of near unity electron spin polarization". The recording serves as a tutorial. Abstract: The inherent low sensitivity of NMR can be overcome by hyperpolarization techniques, which increase the polarization of nuclear spins far beyond the Boltzmann equilibrium. One such method is dynamic nuclear polarization (DNP), which consists of transferring the high polarization of unpaired electron spins to surrounding nuclear spins via microwave irradiation. In the case of dissolution DNP (dDNP), the sample is hyperpolarized in the solid state at low temperature (1-2 K) and moderate magnetic field (3-7 T), where the Boltzmann polarization of electron spins approaches unity, translating into equally high nuclear polarization under DNP. In addition to yielding high nuclear polarization, the high electron polarization has other interesting consequences for NMR. Indeed, as the electron polarization tends towards unity, the electron flip-flop probability vanishes, an effect sometimes referred to as “bath quenching”. By switching on and off microwave irradiation (microwave gating), one switches on and off electron flip-flops and hence paramagnetic relaxation. This has been shown to have a dramatic effect on transverse nuclear relaxation and on nuclear spin diffusion. In this talk, I will review the basic concepts of paramagnetic relaxation and its dependence on electron polarization. I will then present experiments where we used microwave gating to perform efficient CP, to detect EPR properties indirectly via NMR properties, and finally to study nuclear spin diffusion in the vicinity of electron spins. Speaker's biography: 2014- Undergraduate and Masters, EPFL (Switzerland). Thesis with Prof. Bodenhausen 2022- PhD, CRMN Lyon (France), with Prof. Sami Jannin Follow Dr. Stern's work here: Twitter:   / quentinchapp   Google scholar: https://scholar.google.fr/citations?u... Current organizers: Adrian Draney (Creighton University Chemistry) Amrit Venkatesh (Lyndon Emsley Lab, EPFL) Asif Equbal (New York Uni., Abu Dhabi) Blake Wilson (Robert Tycko Lab, NIH) Michael Hope (Lyndon Emsley Lab, EPFL) Mouzhe Xie (Maurer Lab, University of Chicago) Nino Wili (Niels Chr Nielsen Lab, Aarhus University) Tamar Wolf (Lucio Frydman Lab, Weizmann Institute)