ESR pumping experiments in spin-polarized atomic hydrogen

Pumping experiments were carried out in atomic hydrogen using an ESR technique. A model of the decay of the four hyperfine states in the presence of a moderately strong resonant microwave field is described and compared with experimental results. The results indicate that because of spin-exchange relaxation, it is difficult to influence the nuclear polarization of the lower hyperfine states by means of ESR pumping. The model is applied to the design of an ESR-operated beam source of spin-polarized atomic hydrogen. We estimate that in our experiments the maximum flux of particles ejected from the source was 5×${10}^{13}$ ${\sec }^{\mathrm{-}1}$.