Frequency-Swept Integrated and Stretched Solid Effect Dynamic Nuclear Polarization

Abstract

We investigate a new time domain approach to dynamic nuclear polarization (DNP), the frequency-swept integrated solid effect (FS-ISE), utilizing a high power, broadband 94 GHz (3.35 T) pulse EPR spectrometer. The bandwidth of the spectrometer enabled measurement of the DNP Zeeman frequency/field profile that revealed two dominant polarization mechanisms, the expected ISE, and a recently observed mechanism, the stretched solid effect (SE). At 94 GHz, despite the limitations in the microwave chirp pulse length (10 μs) and the repetition rate (2 kHz), we obtained signal enhancements up to ∼70 for the SE and ∼50 for the ISE. The results successfully demonstrate the viability of the FS-ISE and SE DNP at a frequency 10 times higher than previous studies. Our results also suggest that these approaches are candidates for implementation at higher magnetic fields.

Time-optimized pulsed dynamic nuclear polarization

“…For example, NOVEL ( 15 , 18 , 19 ) requires that the electron Rabi frequency, ω 1S , matches the nuclear Larmor frequency ω 0I (ω 1S = ω 0I ) for optimal polarization transfer. This motivated us to search for different strategies to circumvent the direct dependence on the magnitude of the Rabi frequency, and we described two low-power alternatives, off-resonance NOVEL ( 20 ) and frequency-swept integrated SE ( 21 , 22 ). Both approaches yielded significant enhancements using only a fraction of microwave power required by NOVEL.…”

Brute-force solvent suppression for DNP studies of powders at natural isotopic abundance

“…The recent development of high-field dynamic nuclear polarization (DNP) has enabled a wide range of molecular systems to be thoroughly investigated. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] These results have been obtained thanks to the development of hardware, [17][18][19][20][21][22][23][24][25] polarizing agents, [26][27][28][29][30][31][32][33] and theory. [34][35][36][37][38][39][40][41] Among these developments, the study of samples at natural isotopic abundance thrived, [42][43][44][45][46] especially as a result of efficient methodologies for sample preparation.…”

High-Field Magic Angle Spinning Dynamic Nuclear Polarization Using Radicals Created by γ-Irradiation

“…We are optimistic that samples with high radical concentrations may be amenable to future frequency swept microwave or time-domain DNP schemes currently under development. [54][55][56][57][58]…”