  In a recent publication [arXiv:2010.14579], we introduced a new type of
atomic magnetometer, which relies on hydrohalide photo-dissociation to create
high-density spin-polarized hydrogen. Here, we extend our previous work and
present a detailed theoretical analysis of the magnetometer signal and its
dependence on time. We also derive the sensitivity for a spin-projection noise
limited magnetometer, which can be applied to an arbitrary magnetic field
waveform.
