We studied the efficiency of net magnetization enhancement in photo-SABRE by conducting experiments according to protocol 1 shown in Figure with the 𝜏 () set to zero. Without light irradiation during pH2 bubbling we detected polarization only of cis-ABZ, which is consistent with our previous results (Fig. .2). Applying light irradiation during pH2 bubbling we observe polarization of both cis-ABZ and trans-ABZ (Fig. .3). It is noteworthy that while we efficiently transfer SABRE polarization to trans-ABZ we still detect polarization of cis-ABZ at almost the same level as without light. To assess the signal enhancement 𝜖 for 1 H and 15 N nuclei we calculated the ratio of the signal obtained with SABRE to the corresponding signal in the thermal equilibrium at 9.4 T (Fig. .1). For 13 C nuclei we used the net signal of the solvent CD3OD (24.7 M) as a reference. The signal enhancements 𝜖 at 9.4 T and the polarization levels P are presented in table . We also performed experiments illustrating the unique ability of trans-15 N2-ABZ to preserve SABRE hyperpolarization as a long-lived singlet order of the 15 N spin pair for tens of minutes.