Limitations of optically pumped spin‐exchange‐polarized targets

The effects of spin‐exchange collisions on the polarization of dense spin‐polarized samples of hydrogen and deuterium are analyzed. It is shown that even in large magnetic fields spin‐exchange collisions transfer angular momentum between the electrons and the nuclei. This effect has important implications for the operation of spin‐polarized targets and sources of hydrogen and deuterium. For the specific case of sources that are spin‐polarized by spin‐exchange collisions with optically pumped alkali atoms, spin‐exchange not only polarizes the hydrogen and deuterium electron spins, but polarizes the nuclear spins as well.