Time-optimized pulsed dynamic nuclear polarization.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30746482.
- Also identified by DOI 10.1126/sciadv.aav6909 and PMC identifier 6357739.
- Licence recorded as CC BY-NC.
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Abstract
Pulsed dynamic nuclear polarization (DNP) techniques can accomplish electron-nuclear polarization transfer efficiently with an enhancement factor that is independent of the Zeeman field. However, they often require large Rabi frequencies and, therefore, high-power microwave irradiation. Here, we propose a new low-power DNP sequence for static samples that is composed of a train of microwave pulses of length τ<sub>p</sub> spaced with delays <i>d</i>. A particularly robust DNP condition using a period τ<sub>m</sub> = τ<sub>p</sub> + <i>d</i> set to ~1.25 times the Larmor period τ<sub>Larmor</sub> is investigated which is a time-optimized pulsed DNP sequence (TOP-DNP). At 0.35 T, we obtained an enhancement of ~200 using TOP-DNP compared to ~172 with nuclear spin orientation via electron spin locking (NOVEL), a commonly used pulsed DNP sequence, while using only ~7% microwave power required for NOVEL. Experimental data and simulations at higher fields suggest a field-independent enhancement factor, as predicted by the effective Hamiltonian.