  Several efforts have been made to polarize the nearby nuclear environment of
nitrogen vacancy (NV) centers for quantum metrology and quantum information
applications. Different methods showed different nuclear spin polarization
efficiencies and rely on electronic spin polarization associated to the NV
center, which in turn crucially depends on the inter-system crossing. Recently,
the rates involved in the inter-system crossing have been measured leading to
different transition rate models. Here, we consider the effect of these rates
on several nuclear polarization methods based on the level anti-crossing, and
precession of the nuclear population while the electronic spin is in the ms = 0
and ms = 1 spin states. We show that the nuclear polarization depends on the
power of optical excitation used to polarize the electronic spin. The degree of
nuclear spin polarization is different for each transition rate model.
Therefore, the results presented here are relevant for validating these models
and for polarizing nuclear spins. Furthermore, we analyze the performance of
each method by considering the nuclear position relative to the symmetry axis
of the NV center.
