Fig. 2. Experimental and spectral distinction between magnetization and singlet spin order.

(A) Experimental procedure. The sample is hyperpolarized by bubbling parahydrogen (p-H₂) through the solution in the NMR tube for 5 min and subsequently transferred into the high-field magnet for detection. If the hyperpolarization/bubbling is performed in a magnetic shield at ~6 mG, z-magnetization is created (black). If the hyperpolarization/bubbling is performed in the laboratory field anywhere between ~0.1 and ~1 kG, singlet order is created (blue). (B) Z-magnetization and singlet spin order can easily be distinguished based on their spectral appearance. a.u., arbitrary units. Z-magnetization produces an in-phase quartet (black). Singlet order gives an anti-phase quartet (blue). The spin system parameters for the ¹⁵N₂ two-spin system are J_NN = 17.3 Hz and Δδ = 0.58 parts per million.