Production of Spin-Polarized Molecular Beams via Microwave or Infrared Rotational Excitation

We show how small molecules in an intense and cold molecular beam can be highly nuclear-spin polarized via microwave or infrared rotational excitation schemes, followed by hyperfine-induced quantum beats. Repumping schemes can be used to achieve polarization above $90%$ in cases where single-pumping schemes are insufficient. Projected production rates in excess of 10²¹ s⁻¹ allow applications including nuclear-magnetic-resonance signal enhancement, and spin-polarized nuclear fusion, where polarized nuclei are known to enhance D-T and D-³He fusion cross sections by $50%$.