Fig. 1: High field liquid-state NMR spectrometer and performance.
From: Overhauser enhanced liquid state nuclear magnetic resonance spectroscopy in one and two dimensions
a Schematic of the setup and zoom-in-view on the DNP probe. ν and PMW are MW frequency and power, respectively. b MW pathway and geometry of sample irradiation with mirrors (M). k is the vector indicating the wave propagation direction, (E, B) the electric and magnetic field vectors, respectively. c 263 GHz continuous wave (CW) electron paramagnetic resonance (EPR) spectra of various radicals: galvinoxyl 1,15N-labeled nitroxide 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPONE) 2 and α,γ-bis-diphenylen-β-phenylallyl (BDPA) 3 in toluene, showing the spread of EPR resonance frequencies at 9.4 Tesla (Table 1). d Sketch of the sample arrangement, radio frequency (RF) coils for NMR, and MW irradiation from mirror M3 onto the sample. Concentric quartz tubes confine the sample into a thin layer of thickness d. e Pulse sequence for 1D 13C NMR with 1H decoupling using the WALTZ16 pulse sequence (“Methods”) and the recycle delay (RD). f DNP-NMR spectrum of 200 mM 13CHCl3 4 (13C enriched) in CCl4 doped with 10 mM of PA (TEMPONE-15N-d16) (red, 4 scans) and Boltzmann equilibrium spectrum (blue, 32 scans). g DNP-NMR spectrum of the C2-C4 positions of 13C6-fluorobenzene 5 (c ≈ 500 mM, c(PA) ≈ 25 mM in CCl4) recorded (red, 32 scans) and Boltzmann spectrum (blue, 32 scans). Inset shows simulation (black) of the spectrum (blue and red) according to the literature values61. Error in enhancements ε are estimated 10–15%. Sample temperature T was ~300 K, microwave power PMW ≈ 40–50 W. Figure partially reproduced from the PhD Thesis of one author62. Source data are provided as a Source Data file60.
