Fig 1

Hyperpolarization methods grouped by polarization sources 3."

Fig 2

Overhauser effect: (a) Schematic representation of four energy levels and their populations (size of gray bars) at thermal equilibrium. (black and red arrows indicate electron spins and nuclear spins, respectively) (b) Population distribution with the electron saturation transition at the microwave irradiation (ωm = ωe). (c) Population distribution with the cross relaxation."

Fig 3

Solid effect: (a) Schematic representation of four energy levels and their populations (size of gray bars) at thermal equilibrium. (λ1* = λ1 + qλ2, λ2* = λ2 − qλ1, λ3* = λ3 − qλ4, λ4* = λ4 + qλ3, q indicates mixing factor) (b) Microwave irradiation at ωe + ωn leads to positive enhancement. (c) Microwave irradiation at ωe − ωn leads to negative enhancement."

Fig 4

Cross effect: (a) Schematic representation of eight energy levels and their populations (size of gray bars) at thermal equilibrium. (black and red arrows indicate electron spins and nuclear spins, respectively) (b) Saturation of the allowed EPR transitions for electron 1. (c) Zero quantum transition of the electron 2 and nucleus leads to negative enhancement. (d) Saturation of the electron 2 and double quantum transition of the electron 1 and nucleus leads to positive enhancement."

Table 1

Four common DNP mechanisms 6."

Fig 5

(a) Process of spin-exchange optical pumping 25. (b) Orbital structure, fine structure and hyperfine structure of 85Rb 27. (c) 85Rb is hyperpolarized with irradiation of left circularly polarized light (hyperfine structure is ignored because of pressure broadening) 25. (d) 85Rb hyperpolarization in the presence of N2 25."

Fig 6

Level diagram of (a) He including ground state, metastable state, and excited state; (b) hyperfine structure of metastable state and excited state of 3He 38. (c) hyperpolarization of 3He with the irradiation of C8 line 25. (b) Adapted from Springer publisher."

Fig 7

Scheme of optical pumping of semiconductors 25."

Fig 8

Scheme of continuous-flow apparatus for 85Rb-129Xe SEOP 27."

Fig 9

MRI of lung using 129Xe 46. Reprinted with permission from Ref. 46, Copyright (2012) Wiley Periodicals, Inc."

Fig 10

(a) Level diagram of molecular crystal. Circle sizes stand for the population of Tx, Ty, Tz. (b) Scheme of nitrogen-vacancy (NV) center, grey and black balls stand for carbon, blue is nitrogen, and green is vacancy. (c) Zero field splitting (ZFS) and Zeeman splitting of NV center. (d) Scheme of optical electron polarization of NV center 60. Adapted from WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim publisher."

Fig 11

Mechanism of CIDNP 77. Adapted from Elsevier publisher."

Fig 12

(a) CIDNP net (bottom) and multiplet effects (top) in the photoreaction of excited xanthone with triethylamine in acetonitrile. Shown are spectra of the product N, N-diethylvinylamine (for the formula, see inset); left half, signals of HX; right half, signals of HA and HB); (b) level and population diagram of net (bottom) and multiplet (top) effects 77. (a) Adapted with permission from Ref. 79. Copyright (2012) Springer-Verlag Berlin Heidelberg; (b) Adapted from Elsevier publisher."

Fig 13

(a) Principle of a CIDNP experiment without time resolution; (b) A time-resolved CIDNP experiment 81. Adapted from Elsevier publisher."

Fig 14

Three mechanisms (TSM, DD, DR) to produce solid state photo-CIDNP effects 94. Adapted with permission from Ref. 94. Copyright (2012) American Chemical Society."

Fig 15

Energy levels of the radical pairs in electron-electron-nuclear three-spin mixing. The four quantum states of the S-T0 manifold are split due to the differences of the Zeeman interaction of both electron spins, the hyperfine coupling to the nuclear spin, the nuclear Zeeman interaction, and the coupling between the two electron spins 95, 96. Adapted from AIP publisher and Elsevier publisher."

Fig 16

13C MAS NMR spectra of quinone depleted RCs of R.sphaeroides R26 (left) and WT (right) in the dark (black) and under illumination (red) at 17.6 T (a), 9.4 T (b), 4.7 T (c), and 2.4 T (d) 94. Adapted with permission from Ref. 94. Copyright (2012) American Chemical Society."

Fig 17

Level diagrams of AX spin systems: (a) standard NMR; (b) PASADENA; (c) ALTADENA 111. Adapted from Elsevier publisher. "