Previous experiments with thermal polarization showed that spin-locking both the 1 H and 15 N nuclei of trans-15 N2-ABZ provides the longest lifetime of the SO. With photo-SABRE, we measured SO relaxation time equal to 1480 ± 80 s (Fig. .), which considerably outruns the previously published results for the longevity of SO in thermally polarized trans-15 N2-ABZ (about 1000 s). Moreover, the SO relaxation time in our experiments is about 150 times longer than T1 relaxation time of 15 N at 9.4 T (10.8 ± 0.2 s) and seven times longer than T1 of 15 N at 0.1 T (198 ± 2 s) (Fig. ). Such prolonged lifetime of spin order in SABRE experiment is surprising, as in the conventional SABRE experiments the substrate undergoes the continuous exchange with the catalyst, which intensifies the decay of hyperpolarized spin order. However, in photo-SABRE, the trans-15 N2-ABZ does not exchange with the catalyst in the absence of light, which allows storing hyperpolarization in its singlet order for almost half an hour.