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Electron Decoupling with Chirped Microwave Pulses for Rapid Signal Acquisition and Electron Saturation Recovery
Author(s) -
Alaniva Nicholas,
Saliba Edward P.,
Sesti Erika L.,
Judge Patrick T.,
Barnes Alexander B.
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201900139
Subject(s) - spins , electron , decoupling (probability) , atomic physics , microwave , magic angle spinning , nuclear magnetic resonance , polarization (electrochemistry) , hyperpolarization (physics) , materials science , magic angle , chemistry , molecular physics , physics , nuclear magnetic resonance spectroscopy , condensed matter physics , engineering , quantum mechanics , control engineering
Dynamic nuclear polarization (DNP) increases NMR sensitivity by transferring polarization from electron to nuclear spins. Herein, we demonstrate that electron decoupling with chirped microwave pulses enables improved observation of DNP‐enhanced 13 C spins in direct dipolar contact with electron spins, thereby leading to an optimal delay between transients largely governed by relatively fast electron relaxation. We report the first measurement of electron longitudinal relaxation time (T 1e ) during magic angle spinning (MAS) NMR by observation of DNP‐enhanced NMR signals (T 1e =40±6 ms, 40 m M trityl, 4.0 kHz MAS, 4.3 K). With a 5 ms DNP period, electron decoupling results in a 195 % increase in signal intensity. MAS at 4.3 K, DNP, electron decoupling, and short recycle delays improve the sensitivity of 13 C in the vicinity of the polarizing agent. This is the first demonstration of recovery times between MAS‐NMR transients being governed by short electron T 1 and fast DNP transfer.