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. 2015 Sep 25;6:8456. doi: 10.1038/ncomms9456

Figure 2. Hyperpolarization of a first-shell nuclear spin using a MW-driven, optically pumped nitrogen-vacancy centre.

Figure 2

Experiments were conducted by orienting a magnetic field Inline graphic=4.04 mT at θ≈42° and φ≈85° polar and azimuthal angles with respect to the zero-field tensor D0 of the NV centre. The effective 13C Larmor is then δ≈8.8 MHz, while the first-shell hyperfine interaction is Δ≈130 MHz. Two MW power strengths were calibrated corresponding to Rabi frequencies of Ω≈1.4 MHz<8.8 MHz≈δ (ac) and Ω≈11.9 MHz>8.8 MHz≈δ (df) corresponding to the selective and the Λ-regime, respectively. Blue, red and green colours represent the states Inline graphic, Inline graphic and Inline graphic respectively. (a,d) Optically detected experiments determining the eigenstate populations at the end of the polarization phase during 30 μs as a function of the MW frequency ω. (b,e) Predicted eigenstate population spectra calculated without free parameters, that is, using calibrated and known couplings, and a hyperfine tensor was taken from ref. 29. In the selective regime (ac), the Inline graphicpopulation spectrum exhibits two peaks corresponding to the Inline graphic transition frequencies, whereas in the Λ-regime (df) the Inline graphicpopulation spectrum has a single peak centred half-way between the Inline graphic transition frequencies. (c,f) Derived 13C polarization spectra confirming the polarization directions along the Inline graphic-state axis (c) and the Inline graphic-state axis (f) for the selective and Λ-regimes, respectively.