To analyse singlet-triplet conversion in H 2 and to optimize the pulse sequences we used spin dynamics simulations and additionally took into account exchange of H 2 or SABRE substrate. is the rate of association of H 2 to 𝑘 𝑎𝑠 form the Ir-based complex and is the dissociation rate of 𝑘 𝑑𝑖𝑠 molecular hydrogen from the complex. This model is sufficient to simulate singlet-triplet conversion, which gives rise to hyperpolarized oH 2 . To carry out these simulations, we introduce in the rotating frame (this is done to ease 𝐻 𝑓,𝑏 numerical calculations and to get rid of the large nuclear Zeeman interaction with the field, which is parallel to the -𝐵 0 𝑧 axis). For simplicity, we take the frequency of the rotating frame equal to the NMR frequency of free H 2 , so that and