Electron-spin resonance, nuclear polarization, and spin relaxation of spin-polarized atomic hydrogen

Electron-spin-resonance measurements of spin-polarized hydrogen are presented. Excellent signal-to-noise ratio, previously obtainable only in pressure studies, allows quantitative fits to the separate a and b (proton up and down) decays of the nuclear-spin-polarized samples, yielding separate temperature dependences of the recombination rate constants $K_{\mathrm{aa}}$ and $K_{\mathrm{ab}}$. Spin relaxation due to magnetic particles in the substrate is studied for different thicknesses of solid ${\mathrm{H}}_2$ wall coating, and the results are compared with a new theoretical model.